The authors describe four cases of paternity suits where the paternity was not ruled out according to HLA antigens and was ruled out in signs of erythrocyte, serum and enzyme systems, although the capacity of the HLA system was high, in two instances above 98%. From the results ensues that it is useful to supplement the examination by erythrocyte, serum and enzyme systems in those instances where HLA typing was performed first and the man was not ruled out.