The purpose of this study was to determine the role of proteinuria on pregnancy outcome in 444 hypertensive women with singleton pregnancies. The patients were divided into three hypertensive groups: 98 with chronic hypertension, 199 with nonproteinuric gestational hypertension, and 147 with proteinuric preeclampsia and chronic hypertension with superimposed proteinuric preeclampsia. The presence of increased proteinuria (greater than 0.3 gm/L) predicted an adverse pregnancy outcome. Furthermore, the majority of small-for-gestational-age infants occurred in the group with proteinuric preeclampsia (52%), whereas the rate of small-for-gestational-age infants was 18% and 12% in the group with nonproteinuric gestational hypertension and chronic hypertension, respectively. The group with chronic hypertension did not show any increased risk for fetal outcome. Perinatal mortality rate was extremely poor in the group with proteinuric preeclampsia at 129 per 1000, four times higher than those of the other two groups.