During the 18-year period from 1971 through 1988, 37 women whose pregnancies were complicated by moderate or severe renal insufficiency were managed at Parkland Memorial Hospital. Common maternal complications included anemia, chronic hypertension, and preeclampsia. Perinatal complications included midpregnancy losses and low birth weight from preterm delivery, fetal growth retardation, or both. Despite the high incidence of maternal morbidity, 85% of pregnancies in the 26 women with moderate renal insufficiency resulted in a live-born infant; there was one stillbirth and no neonatal deaths. Of the 11 women with severe disease, seven were delivered of live-born infants after greater than or equal to 26 weeks' gestation. Although six of these 37 women had worsening renal function during pregnancy, it seems unlikely that pregnancy per se caused this. More importantly, in four of these six women and in four others who had stable function throughout pregnancy, end-stage renal disease developed within a mean of 4 years after delivery. In 14 women blood volume was determined during pregnancy, and whereas those with moderate disease had normal volume expansion, women with severe disease had significantly attenuated expansion. Finally, serial creatinine clearances did not increase during pregnancy in half the women with moderate insufficiency and none with severe dysfunction.