Glomerulocystic kidney disease (GCKD) is a relatively rare condition with both a sporadic and familial occurrence. Pathologically, GCKD is characterized by cystic dilatation of Bowman's space and the initial proximal convoluted tubule. As a heritable disorder, GCKD has primarily been recognized in infants with a family history of classic, autosomal dominant polycystic kidney disease (ADPKD). Dominantly transmitted GCKD associated with either hypoplastic or normal-sized kidneys has also been reported in older children and adults. A large, three-generation African-American family with familial GCKD is characterized. Of the 20 individuals available for study, seven affected individuals were identified by renal sonogram or renal histopathology. GCKD in this family segregates as an autosomal dominant trait as evidenced by its apparent transmission from a father to his sons. A set of directed linkage strategies indicates that the distinctive GCKD phenotype in this family results from a dominantly acting mutation that disrupts a genetic locus distinct from the ADPKD loci, PKD1 and PKD2, as well the human homologue of mouse jcpk mutation, a newly described murine GCKD. These analyses are the first known genetic studies conducted in a family with heritable GCKD and postinfantile age of onset.