I don't think that they are 100 percent accurate, but they can tell you some kind of picture about yourself. Three of my grandparents are Slovak and my fourth is a mix of the british isles and central European countries. I took an autosomal test with ancestry.com and I came back as 29% Scandinavian, 63% Eastern European and 8 percent uncertain. I had my parents take the same test and my mother who is half Slovak and half(the fourth grandparent) came out as 54% Eastern European and 43% central European. My Father who is full Slovak came out as 45% Eastern European, 34% Central European and 21% Finnish Volga Ural. As you can see there is some confusion. How did I get so much Scandinavian when My parents have none. Well if we think about it a little maybe its not so confusing. We know central Europe (Germany and Franice in this test)is a mix of Germanic people from Scandinavia who came south and mixed with celtic type peoples. So Autosomally my parents showed up as having Central European because they have that pattern of a mix of celtic and Germanic genes. However maybe I only got the Germanic segments of those genes which best matches me with Scandinavian people. Also the Finnish/Volga Ural, a region which stretches from finland to the Caucasus has a lot of Slavic genes wich probably my father has in common with eastern Slavic people, and that is probably the 8 percent% unkown in me. This is probably the best way to look at autosomal testing. It is somewhat accurate but not perfect. It depends heavily on the testing companies database, and what the conclude as a homogenous region.