Our hospital serves poor, inner-city women who have a 17% preterm delivery rate. Middle-class women in San Francisco at high risk for preterm delivery have benefited from an antepartum program which emphasized patient education and close follow-up. Using a controlled, randomized design, we are investigating the impact of similar interventions. Patients determined to be at high risk before 18 weeks' gestation on the basis of the Creasy system are randomly assigned to the Preterm Labor Prevention Clinic or serve as high-risk controls. Sixty-four women assigned to the Preterm Labor Prevention Clinic and 68 high-risk control women have been delivered of their infants. No significant differences were noted for the percentages of preterm infants, mean gestational age, or birth weight. Preterm rupture of the membranes accounted for 40% of preterm deliveries in all high-risk patients. Thirty percent of preterm births were indicated for maternal or fetal reasons. The remaining 30% represented failure of tocolytic therapy.