It has been suggested that average genetic similarity, as assessed by
blood genetic markers, could influence mate choice in humans. In the p
resent study, average genetic similarity was assessed in 183 couples s
ubmitting to paternity determinations in relation to six blood group s
ystems and three HLA loci. Couples in which the putative father was ex
cluded were compared with those in which such exclusion did not occur,
and real couples were compared to random pairs. The differences were
all statistically non-significant. Possible reasons for the different
results found in the previous sample and in the present study are cons
idered.