The distribution of human leucocyte antigens (HLA) was analyzed in 35 patients with severe preeclampsia and compared with that in the general population in the Niigata district of Japan. The frequency of patients with HLA CW7 was significantly higher than that of the general population of this area (p < 0.05, Chi-square test). The frequency of those with HLA-DR6 (DR6, DR13 and DR14) was also significantly greater compared with the general population (P < 0.05, Chi-square test), while that of those with DR4 was significantly lower (P < 0.05, Chi-square test). The compatibility of HLA antigens in spouses was also analyzed in 20 patient couples and 26 normal fertile couples, and there was no significant difference. Thus it is suggested that HLA antigen systems might be involved in the genesis of preeclampsia.