The effect of intramuscular injections of sparteine sulfate on the pregnant term uterus in 36 patients was studied by a continuous recording of amniotic fluid pressure. Twenty-two patients were given 150 mg. doses of sparteine sulfate and 14 received 75 mg. doses. The spontaneous labors of an additional 15 patients were recorded as controls. Thirteen patients receiving 150 mg. doses had episodes of hypertonus, 2 of which were prolonged tetanic contractions. There were 4 episodes of hypertonus in the 14 patients receiving 75 mg. doses. It was concluded that the 150 mg. dose of sparteine sulfate was excessive and, as with other antepartum oxytocics, constant attendance of the patient under the supervision of a physician was necessary, regardless of dosage involved. © 1969.