Oct 2019 Update revises Promethease recommendation; Oct 2018 Update adds Alzheimer comments.I had DNA analysis from 23andme. My wife had DNA analysis from both Ancestry(Anc) and 23andme. This review is my comparison of the two. I now do not recommend secondary analysis of your results by Promethease, see further discussion at end of this review. Basically I like 23andme. For developing an ancestry tree, Ancestry.com is MUCH better IF you signup separately for Ancestry's subscription search service. Do not use Anc & Promethease for Alzheimer's - see discussion at end of this review.TAKING TEST and SIGNUP – Very similar test taking. 23’s signup was more secure. Anc’s was easier, but they automatically put my wife’s test on my previously existing Ancestry account.Waiting on RESULTS – Both send emails confirming sample receipt and when results were available. After logon, 23 provided step by step progress reports on the analysis process. The analysis process itself took about 10 days, including a holiday weekend. Total wait time was 3-4 weeks. Anc took 5 or so days longer than 23.WEB SITE SECURITY – 23 is better. 23 requires a typical logon and password to get to the site. Anc automatically remembers your logon and password and just opens up when you go to the site. However, actually downloading your DNA file from Anc requires a full sign-on and confirmation link via your e-mail..Ethnic Origin Analysis – I think 23 is more correct. Both 23 and Anc keep updating their Ethnic origin results. Note the results are only approximate considering the accuracy ranges provided.DNA RELATIVE IDENTIFICATION – Recognizing that allocation of relatives to 1st, 2nd and 3rd cousins is somewhat imprecise. For my wife, 23 identified 4 second cousins and about 32 third cousins. Anc identified 1 first cousin, 2 second cousins and 9 third cousins. 23 also has ‘cousins’ outside the USA (in my case in the UK) which are really valuable contacts for ancestry searching. The web site does not directly identify a cousin’s location but you can easily guess this from supplementary info optionally provided by the cousin on 23’s site.DNA RELATIVE CONTACT and ANALYSIS – Anc provides the e-mail for a contact and shared ancestors for each DNA relative. You get a lot more when you pay for their regular Ancestry services, see below. 23 provides an internal messaging application for communicating with contacts. The application works but is rudimentary and unsuitable for more than brief messages (especially with MS Edge); exchanging e-mail address’s after contact is more satisfying. Both have a couple levels of ‘sharing’ (aka privacy). Both have tools for grouping contacts.Anc provides a powerful tree searching tool IF you subscribe to the regular Ancestry service. This is expensive, in the range of $200/year, but less with special offers. Given the moderate ‘tools’ in their basic DNA service, I view their DNA analysis as an (effective) teaser for their subscription service. UPDATE: I did signup for the Ancestry services and they are great. Specifically, with a subscription their DNA site shows a contacts pedigree chart if that contact already has built an Anc family tree. This is MASSIVELY better than 23's unsorted list of surnames. When you search for a particular name it searches all of the connected family trees - this is exceptionally useful.MEDICAL INFO – Anc provides no medical info. In late 2016 23 had two test options - $100 for just the ancestry service and $200 for ancestry plus medical. As of Sept 2018, 23 provides FDA approved reports on your risk of 9 medical conditions, including Alzheimer's, plus several genetic carrier reports. Their discussion/explanation of your risks for these conditions is specifically approved by the FDA and is understandable, informative, and useful. [Update ANC now advertises health results - I have not tried this]If you are so inclined, you can participate (answer a lot of online questions) in 23’s medical research. This is probably 20 ten minute questions sessions. I did this and feel like it was useful for medical research.Analysis of you DNA results by Promethease, a third party service, provides some medical info.[October 2019 Update] In late 2019 Promethease was bought by MyHeritage, an Israeli Company. They have advised that they will use the DNA profiles downloaded to them for DNA ancestry searches, including searches by police departments. I personally am uncomfortable with this. Further in early 2019 Promethease stopped providing reports for a number of SNP's potentially related to drug usage, apparently due to pressure from the FDA. These are among the MOST useful (actionable) results. For these reasons I think Promethease is now of substantially less value. Perhaps MyHeritage will reinstate the deleted SNP's, but I doubt it. Use Promethease with caution. Note that I have NOT updated the remainder of the Prom discussion to reflect the above comments.CONNECTION to PROMETHEASE – Promethease (Prom) is a third party service that assess’s your detailed DNA results from either 23 or Anc and provides a detailed medical risk report. Go to the Prom site to get started. The download process is not too difficult. In Oct 2018 cost is $12 per report.PROMETHEASE RESULTS –Prom generates 20,000 or so reports (hits) from the 700,000 or so genes that are tested by 23 and Anc. 23 and Anc test a different set of genes, although they mostly overlap. For my wife’s test from both 23 and Anc the corresponding Prom reports were about 85% the same for the 40 most significant hits (Prom magnitude 2.5 and above). There were 5 or 6 unique hits in the top 40 for each report. I judge that the unique hits were about equally important, between 23 and Anc - none were critical.[Nov 2017 Update] In October 2017 I resubmitted by 2016 23 test to Prom. About 15% of the hits were changed. A couple unusual hits were deleted. A very significant change was that one gene comment changed from 'increased risk of Type 1 diabetes' to '18x risk of Type 1 diabetes'!!! I read up on this. It turns out that the genetic - diabetes risk/connection is currently a very hot and complex research topic. The relevant research report was published in 2017. My suggestion is to update your Prom report every year or two if there are concerns.USING PROMETHEASE – IMPORTANT – Use of general DNA analysis to identify general medical conditions is an emerging (not well developed) technology/business. My guess is that the info provided by Prom is perhaps 30% or so of what will be available in 10 years or so. I regard the info provide as indicative, definitely not complete and possibly incorrect (due to either testing error or interpretation error).Having said that, it is interesting, likely useful and potentially lifesaving. The information will be disturbing (negative), but in most cases not surprising. I think most people will be able to absorb the info without getting too stressed out. If you are a hypochondriac, this could be a problem. If you want a chance of good news, you can write down the stuff your are concerned about ahead of time, and then see if they actually shows up.My comments for using the report are:• Make sure you download a copy to your PC for future reference, don’t just look at it online.• After you figure out how to use the report, move the '0' Magnitude slider up to a range of 2.5 or so. This will limit you to the top 40 or so hits. Then go down to the bottom of the report and hit the '2X' bar a few times to see all the hits.• You can then hit the ‘Table’ button at the top and print a summary of the hits to help see the big picture. You can also open this table in Excel and modify/save it for a more useful table. If you do this, add a Frequency column if it's not already there.• To me, after Magnitude, the most important factor is ‘Frequency’. This is what percentage of the target population has this condition. If its around 40% or higher, I think it’s already ‘dialed in’ to the normal medical process – it is something your doctor and the medical community will look for in any case. Most of the hits fall into this category. If it’s less than 10%, it’s likely not on your doctors radar screen and you will want to consider if it’s worth mentioning to your doctor.• The second most useful item is the relative increased risk in the item discussion. Recognize that the absolute risk is not provided – for example, the absolute risk might be 1 person in 100,000, so a 1.1 relative risk increase is almost meaningless. On the other hand I looked up AMD (Age Related Macular Degeneration-eye problems) on the internet; it affects 1 in 3 to 5 people by age 80, so 2x risk is really significant. Good to know this ahead of time.• After you assess the top 40, which takes a while, you can expand the Magnitude to it’s full range. Then click on ‘Topics’ and click on sub topics of interest and see if any common concerns emerge. Do the same for ‘Medical Conditions’. This seems like a lot of work but only takes an hour or 2 once you get started. For me the common themes seem to be heart disease, Alzheimer’s and Rheumatoid arthritis – none of which are a surprise.- When you find something that might be relevant you NEED to do supplemental research on the Internet. The Prom report is a brief and simple identification. Fuller understanding can significantly change (reduce?) your concern for the issue. Be aware that there are 'hypochondriac' web sites for some of these issues. I like to start with Wiki, Mayo Clinic and WebMD. Search for the Prom gene name 'rs........'. Then find out what the common term(s) for the gene is e.g. MTFHR and search for that. Write stuff down, gene names can be confusing.• Again, remember this is an emerging technology, so the results will change from year to year. I guess that in 10 years it will be a routine consideration in a physical.IMPORTANT. DO NOT use Prom results from Anc for Alzheimer's. Anc almost always reports zero copies of the Alz APOE4 gene. Prom notes this in their report, but it’s carries a low Magnitude and is easy to miss. In Sept 2018 I did an Anc test and it returned (via Prom), Zero copies of the Alz gene. The Anc and Prom medical results were otherwise similar but slightly less extensive than 23 and Prom.