The chromosomal pattern of 31 specimens of chromophilic renal-cell cancer (RCC), selected according to the criteria mentioned in the classification of Thoenes and Störkel, is presented. A high male preponderance was found (8.7:1). Cytogenetic analysis revealed a typical pattern of numeric alterations specific for this sub-type in the majority of cases (i.e., --Y,+7, +12, +16, +17, and/or +20), which is different from the chromosomal patterns found in other sub-types of RCC. Gain of chromosome 20, as well as loss of the extra copy of chromosome 17 or loss of 17p, was found to be related to the higher-grade chromophilic carcinomas. None of the 14 cases examined by SSCP analysis revealed mutations of the p53 gene, indicating that other genes at 17(p) might be important in the progression of this sub-type of RCC.