The activity of N-acetyl-beta-hexosaminidase was found to be significantly higher in the placentas collected after delivery from women in puerperium with symptoms of prolonged pregnancy or complicated by EPH gestosis, than in placentas from normal pregnancy. Isoelectrofocusing of placenta homogenates showed the presence of isoenzymes A, P and B of N-acetyl-beta-hexosaminidase. Different isoenzyme A patterns in homogenates were observed in placentas obtained from normal and prolonged pregnancies and in those complicated by EPH gestosis.