ABSTRACT: Human leukocyte antigen (HLA) typing was undertaken in 151 unrelated blood donors and in 35 normal couples having at least two living children. We compared observed and expected sharing of HLA antigens at four loci in normal couples. We also compared the observed sharing in couples with the expected sharing in unrelated blood donors if taken two by two and with the sharing observed after 1000 “synthetic matings” of normal couples. No statistically significant difference in HLA sharing appeared between these groups. Furthermore no differences were observed in the probabilities of sharing individual HLA antigens among the different groups. We thus conclude that the observed HLA sharing in normal couples is governed by chance alone and that mating is random in our population.