The etiology of premature rupture of the membranes (PROM) has been investigated in 30 consecutive cases and 30 matched controls. The significance of several possible factors predisposing to this condition is discussed and the obstetric and pediatric outcome reviewed. Significantly increased frequencies of previous genital operations, cervical operations and lacerations were found in the PROM group, which also contained significantly more heavy smokers. The relation between the length of the PROM delivery time interval and the risks of prematurity and infection are discussed. Patients delivered > 24 hours after PROM had significantly more puerperal infections than those with a latent period of > 24 hours. Maternal fever was found to be an unreliable prognostic indicator. The incidence of puerperal infection amounted to 27 per cent in the PROM group. A 12 per cent incidence of proven neonatal septicaemia contributed to a high perinatal mortality rate (17.6 per cent).