Lysine vasopressin and a long-acting analogue N alpha-triglycyl-lysine vasopressin were compared in a prospective randomized double-blind study including 71 women undergoing cold knife conization of the uterine cervix. Hemodynamic and hemostatic variables were studied. N alpha-triglycyl-lysine vasopressin had the following advantages over lysine vasopressin: it gave significantly less skin pallor, becoming evident at a later stage during the operation. The diastolic blood pressure was significantly lower, as also was the incidence of postoperative hemorrhages. Factor VIII related antigen was lower. On the other hand reduction in heart rate (values before conization compared with values during conization) was more pronounced when N alpha-triglycyl-lysine vasopressin was used, but there was no difference in absolute values between the two groups during conization.