Renal cell carcinoma (RCC) occurs predominantly as a sporadic disease but has familial forms. Cytogenetic and DNA deletion analyses show that both sporadic and familial RCC tumors arise as the result of chromosomal deletions in the 3p13-p26 region. von Hippel-Lindau (VHL) disease is a hereditary, multifocal syndrome that includes, among several affected organs, multiple, bilateral renal cysts and RCC. Although the VHL disease gene maps to chromosome 3p25-p26, data indicate that the VHL and sporadic RCC disease genes are likely to be independent. The authors hypothesize that VHL disease manifestations are controlled by mutations in the VHL disease gene and that the onset of VHL-associated kidney cancer is due to a second mutation of the linked sporadic RCC gene.