Three hundred sixty-two pregnant patients at risk for placental insufficiency were evaluated with the oxytocin challenge test (OCT) and urinary estriol determinations. The perinatal mortality in patients with positive tests was 6 times higher than the perinatal mortality in patients with negative tests. Expectant treatment of patients with a positive OCT was associated with a perinatal mortality 6 times higher than if immediate delivery was accomplished. A negative stress test was reassuring, as the risk of death in utero within a week of a negative test was only 0.3%. The combination of low estriol levels and positive OCT was quite ominous, while the presence of normal estriol levels provided reassurance of good perinatal outcome when expectant treatment of a patient with a positive OCT was undertaken. The overall perinatal mortality of the patients in this study was not different from that in the general obstetric population.