Serum cholinesterse activity decreases 30% during pregnancy and remains depressed during the postpartum period. However, succinylcholine recovery is not prolonged in term-pregnant patients. This contrasts with results obtained in other patients with decreased serum cholinesterase activity. To better understand this paradox, the authors compared serum cholinesterase activity and recovery from succinylcholine, 1 mg/kg, in nonpregnant (with and without oral contraceptive use), in term-pregnant, and in postpartum patients. Serum cholinesterase activity was lower in both term-pregnant (3.66 ± 039 U/ml, X ± SE) and postpartum (2.84 ± 035 U/ml) patients than in nonpregnant patients not taking oral contraceptives (5.01 ± 0.33 U/ml,P< 0.05). Cholinesterase activity in postpartum patients also was significantly lower than in nonpregnant patients taking oral contraceptives (4.81 ± 0.63,P< 0.05). In contrast, the time to 25% twitch-height recovery did not differ between term-pregnant (470 ± 56 s) and nonpregnant patients taking (499 ± 29 s) or not taking (501 ± 21 s) oral contraceptives, but was significantly increased in postpartum patients (685 ± 22 s,P< 0.001). The similar duration of action of succinylcholine in term-pregnant patients (with decreased serum cholinesterase activities) and nonpregnant patients may be related to the increased volume of distribution of succinylcholine at term.