A comparison was made between measurement of total fetal activity and biophysical profile as predictors of infection in preterm premature rupture of membranes. Sixty-four patients with premature rupture of membranes, not in labor, between 24 and 34 weeks' gestation were studied. All patients had an amniocentesis and 25 patients were diagnosed as having intra-amniotic infection. The sensitivities of the tests were 96% and 92%, respectively, with specificities of 82% and 59%. Measurement of total fetal activity had significantly better specificity.