OBJECTIVE Our purpose was to determine the efficacy and safety of long-term oral tocolysis with indomethacin or terbutaline sulfate. METHODS Seventy-one patients at 26 to 32 weeks' gestation admitted for preterm labor were prospectively randomized to receive oral indomethacin or terbutaline sulfate after successful intravenous tocolysis. Patients were monitored weekly for cervical change, maternal side effects, amniotic fluid volume, and constriction of the fetal ductus arteriosus. Patients receiving indomethacin were converted to terbutaline at 34 weeks or with the occurrence of fetal ductal constriction or oligohydramnios. RESULTS Of 71 patients randomized six were excluded after randomization. Thirty-three patients were randomized to indomethacin and thirty-two to terbutaline. There were no differences in the percentage of patients achieving 34 weeks of gestation. No differences in neonatal outcome were noted. Nine (27%) fetuses receiving indomethacin had constriction of the fetal ductus arteriosus, and 13 (38%) had oligohydramnios. Most patients on terbutaline reported beta-mimetic side effects (53%), but only one required discontinuation of therapy. CONCLUSIONS Both indomethacin and terbutaline sulfate are effective tocolytics, but major fetal side effects are common with long-term indomethacin use.