Observations were made on 153 preterm infants (25 to 34 weeks' gestation) in an attempt to answer the following questions: dose prolonged rupture of the fetal membranes (ROM) correlate with a decreased frequency of respiratory distress syndrome (RDS) and patent ductus arteriosus, and, if so, what is the duration of ROM required? An analysis of the data indicates that as the duration of ROM is lengthened the incidence of RDS and patent ductus arteriosus decreases. In fact, after 48 hours of prolonged ROM (PROM), there is a virtual absence of RDS. In addition, after 72 hours of PROM, the frequency of patient ductus arteriosus was markedly reduced to only 12 per cent (three of 25 infants). PROM beyond 24 hours was also associated with a significant decrease in deaths (p less than 0.05). Amnionitis occurred in 33 per cent of pregnancies with PROM greater than 48 hours; however, only one infant died of sepsis. These findings support the hypothesis put forth by the others 1-5 that PROM is indeed associated with a decreased frequenct of RDS in preterm infants. Moreover, our findings suggest that PROM greater than 72 hours is associated with a relatively low frequency of patent ductus arteriosus. The question is then raised that perhaps pregnancies less than or equal to 34 weeks' gestation with PROM should be allowed to continue for 72 hours in the absence of amnionitis.