Vecuronium (Org NC 45) was used in 27 parturients undergoing elective cesarean section under general anesthesia. One of the parturients had a twin pregnancy. Neuromuscular transmission was assessed clinically by stimulating the ulnar nerve and observing the contraction of the fingers. An initial bolus of 0.05 mg . kg-1 of vecuronium was injected after recovery from succinylcholine block. Complete neuromuscular block resulted in all cases and lasted for a mean duration of 19.3 +/- 6.02 min. Muscular relaxation was maintained by incremental doses of 0.01 mg . kg-1 of vecuronium. Administration of vecuronium did not cause significant changes in blood pressure, pulse rate, or plasma cholinesterase activity. Also, there was no correlation between the plasma cholinesterase activity and the duration of neuromuscular block of vecuronium. The residual neuromuscular block could be antagonized at the end of the procedure by a mixture of 0.005 mg . kg-1 of glycopyrrolate and 0.025 mg . kg-1 of neostigmine. In all parturients, antagonism was adequate as evidenced by maintained tetanic response (50 Hz for 5 sec) and sustained head lift. Nine infants were delivered before the injection of vecuronium; 19 infants were delivered after its injection. There was no significant difference between the Apgar scores in the two groups, suggesting that vecuronium does not cross the placenta in concentrations that affect the newborn. Vecuronium may be advantageous in parturients undergoing cesarean section under general anesthesia because it maintains cardiovascular stability, is noncumulative, is readily antagonized by neostigmine, has no effect on the plasma cholinesterase activity, and has no deleterious effect on the newborn.