In the present study we have attempted to ascertain the possible existence of an association between antigens of the major histocompatibility complex (MHC) and development of severe preeclampsia (PE). HLA-A, B, C, DR antigens as well as reactivity in one-way mixed lymphocyte culture (MLC) were studied in 40 couples with severe PE, and subsequently compared to 30 normal fertile control couples. No significant differences in the frequencies of HLA antigens were detected between PE and control couples. The frequency of shared HLA-A, B and DR antigens among members of the couples was similar in both groups. The one-way MLC showed normal reactivity of both parental pairs in all combinations tested. Consequent to our data we are unable to support the suggestion that the MHC affects the susceptibility to develop severe PE.