A family is described in which three siblings, born after pregnancies complicated by oligohydramnios, developed renal abnormalities. In the first infant, of 38 weeks gestation, histologic changes were nearly identical to those found in renal tubular dysgenesis (RTD), a recently identified disorder characterized by the absence of recognizable renal proximal tubules. Additional findings include bilateral renal vein thrombosis and marked calvarial bone hypoplasia. The other two gestations were 20 and 22 weeks long. Renal histology in these cases showed nonspecific abnormalities with focal tubular dilatation, decreased tubule formation, and increased interstitial connective tissue. Clearly recognizable proximal tubules were present, though decreased in number. The latter two gestations described herein are the earliest examined in a family with RTD and the renal abnormalities may represent early changes seen in this disorder.