Renal cell carcinoma (RCC) and normal kidney tissues have been examined from 34 patients with sporadic, nonhereditary RCC. Eighteen of the 21 cytogenetically examined tumors (86%) had a detectable anomaly of chromosome arm 3p distal to band 3p11.2-p13, manifested as a deletion, combined with the nonreciprocal translocation of a segment from another chromosome or monosomy 3. Restriction-fragment-length polymorphism analysis showed loss of D1S1 heterozygosity in 16 of the 21 cases (76%). D3S2 heterozygosity was lost in 2 of 11 cases (18%). The variability of the breakpoint between 3p11.2 and 3p13 and the absence of a consistently translocated segment from another chromosome suggests a genetic-loss mechanism, while the activation of a dominant oncogene appears less likely. Together with the previously demonstrated involvement of the 3p14.2 region in a familial case, these findings suggest that RCCs may arise by the deletion of a "recessive cancer gene," as do retinoblastoma and Wilms tumor. The relevant locus must be located on the telomeric side of the D1S1 locus on the short arm of chromosome 3.