Dear Ann, In situations such as this it is highly probable that the match is IBS. I suspect that in 99% of such cases the match is IBS. However, there is always a possibility that a genotyping error in one of your parents' results or in the match's results is preventing one of your parents from appearing as a match to this person. There is also the possibility that the parent who matches this person doesn't share enough HIRs at least 1 cM in length with this match that total at least 20 cMs. This is another criteria that Family Finder has for a match. Sincerely, Tim Janzen -----Original Message----- From: autosomal-dna-bounces@rootsweb.com [mailto:autosomal-dna-bounces@rootsweb.com] On Behalf Of AGilchrest@aol.com Sent: Monday, November 18, 2013 5:23 PM To: autosomal-dna@rootsweb.com Subject: [AUTOSOMAL-DNA] IBS or IBD Hello, If I have a match that has 27.35 shared cM's with the longest block of 9.01 cM and neither of my parents match my match can I say that this match is IBS? Thank you Ann Gilchrest