Serum cholinesterase activities were assessed in pregnant women with different types of hypertension. Two samples of blood were taken (during prenancy and at puerperium) of 20 normal pregnant women (NP), 16 with mild preeclampsia (MPE), 17 with severe preeclampsia (SPE), six with chronic hypertension plus preeclampsia (CHT+PE) and seven with chronic hypertension (CHT). The enzyme activity declined significantly at puerperium as compared with during pregnancy in the CHT and CHT+PE groups (p < 0.05). Nevertheless, during pregnancy the activities recorded in the CHT group were significantly higher as compared to NP (p < 0.01) and MPE (p < 0.05). At puerperium, cholinesterase activities were significantly higher in: (1) SPE as compared to: NP (p <0.05), CHT (p <0.001) and CHT+PE (p < 0.05), and (2) MPE as compared to: CHT and CHT+PE (p < 0.05). The consequence of the reduction in cholinesterase activity, at puerperium, in the CHT and CHT+PE patients should be established.