beta-Mimetic agents are currently recommended for tocolysis. Serious adverse reactions including maternal death may complicate their use. Prostaglandin synthetase inhibitors are effective tocolytic agents. Reports of potential adverse effects have limited clinical use in North America. This study reports the perinatal outcome in 167 infants exposed to indomethacin used for tocolysis in gestations of less than 35 weeks. The rate of preterm delivery was 41.3% (69 of 167). No cases of premature closure of the ductus arteriosus or persistent fetal circulation were observed. The overall perinatal mortality was 17 per 1000 (1.7%). The results support the view of other uncontrolled reports that a short course of indomethacin used for tocolysis in gestations of less than 34 weeks is without deleterious effects on fetus or neonate. Its ease of administration and maternal safety offer advantages over beta-mimetic agents, and prospective comparisons of both should be undertaken.