Natural cytotoxic activity of lymphocytes from 113 pregnant women presenting one or more symptoms of the toxemic triad (E, P or H) was tested. According to the clinical symptoms, groups EH + H, EP + P and PH + EPH were formed. The control group consisted of 56 healthy pregnant patients. Significantly increased cytotoxicity was observed in toxemic pregnancies with proteinuria (group EP + P, 35.8 +/- 14.3%, P less than 0.001) and with proteinuria and hypertension (group PH + EPH, 27.2 +/- 13.3%, P less than 0.001%), but not in the group with hypertension (EH + H, 13.0 + 9.9%), compared to that of controls (11.0 + 11.5%). The relative number of patients with cytotoxicity greater than or equal to 40% was also higher in groups with proteinuria presenting with or without other symptoms of the disease. Increased cytotoxicity in proteinuric form of gestosis seemed to be independent of the incidence of low birthweight deliveries and intra-uterine growth retardation.