Usually FTDNA, 23andMe and GEDmatch are in pretty close agreement. It appears AncestryDNA uses a somewhat different set of algorithms to analyze exactly the same DNA data and get different results. For me, I use FTDNA and 23andMe results first; GEDmatch results second; and only use the AncestryDNA results that are uploaded to FTDNA and/or GEDmatch. The AncestryDNA segment data is interesting in a general way, but I would not rely on it too heavily. Jim - www.segmentology.org > On Dec 29, 2015, at 7:43 PM, Doris Wheeler via <genealogy-dna@rootsweb.com> wrote: > > My full sister has a match at Gedmatch (22.5 cM, one segment on chromo 1) > and at FTDNA (55.39 cM total, longest block 18.94) that does not show up at > all on Ancestry. The same match for me at Ancestry is 49 cMs across 3 > segments; at FTDNA it is 77.34 total, longest block 37.02; at Gedmatch it > is 64.2 total, longest block 41.8. > > Really frustrating! > > Doris Muller Wheeler