The complement levels were determined in 54 parturient women with EPH gestosis, in 32 normal parturient women and in 24 normal non pregnant women. Complement components: C4, C3c, factor B /Bf/ and C1 inactivator /C1 INA/ were measured by radial immunodiffusion. Peripheral and retroplacental blood were examined. Concentrations of C4, C3c, Bf in peripheral blood of both groups of parturient women were significantly higher than in normal non pregnant women. Peripheral blood of parturient women with EPH gestosis contained significantly higher concentrations of C3c than in normal parturient women. Complement Bf levels of normal parturient women were lower in the retroplacental blood than in the peripheral. The levels of C4 were significantly decreased and C3c increased in the retroplacental blood of parturient women with EPH gestosis when results were compared with retroplacental blood of normal parturient women. Results of present study suggest that complement activation could contribute to the pathogenesis of EPH gestosis.