The medical records of 330 patients treated with terbutaline infusion for the inhibition of preterm labor were reviewed over a five-year period. In patients with intact membranes the results were uniformly good, particularly when treatment was instituted before the 30th week. Half these patients had a prolonged labor of six weeks or more; in most cases of treatment failure complications already existed on admission. In only nine patients (2.7%) terbutaline treatment was stopped due to side effects: predominantly maternal tachycardia or vomiting. Two patients had chest symptoms, but in no case was pulmonary edema diagnosed. The results suggested that a low incidence of severe side effects can be obtained if the following precautions are taken: glucose is used as the infusion medium, instead of sodium chloride; concentrated solutions are given to avoid fluid overload; the patients are carefully controlled; and the infusion is immediately reduced or stopped if signs of severe side effects appear.