After 16 weeks of gestation, amniotic fluid mainly consisted of fetal urine. Therefore, the association of oligohydramnios with fetal urinary tract abnormalities implies severe deterioration of renal function. The relationship of the kidney and amniotic fluid in pulmonary development has been investigated, and fetuses with oligohydramnios starting in the second trimester are considered to have uniformly fatal outcomes. We analysed underlying urological disorders, gestational age at presentation, and ultimate outcomes in 45 fetuses with severe oligohydramnios, and especially focused on clinical courses and prognosis of 7 surviving patients. Clinical and/or autopsy diagnosis included bilateral renal hypodysplasia in 20 patients, urethral atresia with/without prune belly deformity in 9, posterior urethral valve in 6, polycystic kidney disease in 4, hydrometrocolpos in 2, hereditary renal dysplasia in 2, and the others. The average gestational age at detection of severe oligohydramnios was about 30 weeks, ranging from 16 weeks in patient with urethral atresia. Urological disorders of 7 surviving patients consisted of 4 posterior urethral valves, one hydrometrocolpos, one hydronephrosis of the solitary kidney, and one bilateral megaureter. In these 7 patients severe oligohydramnios striated in the third trimester. Four patients required ventilator supports together with the administration of surfactant, but they were weaned in one to 4 days. There was no evidence of pulmonary hypoplasia on chest X-ray films. Urological emergency drainage was necessary in all patients on the day of delivery to 2 days postnatally. One patient with posterior urethral valve developed ESRF 6 months after birth. Two patients have a normal serum creatinine, but another 4 have slight elevation of SCr for their age.(ABSTRACT TRUNCATED AT 250 WORDS)