A group of 41 young patients (age less than or equal to 40 years; mean, 35.7 years) and a group of 34 old patients (age greater than or equal to 80 years; mean, 82.4 years) who underwent operation for renal cell carcinoma between 1970 and 1986 were compared. Sex, grade, and DNA ploidy pattern distributions were similar between the groups. Granular cell and papillary cancers with lower stages at presentation were more common among the young. In patients with high-stage disease, 73 percent of the older group but none of the younger had DNA diploid tumors. Low-stage clear cell carcinoma caused cancer death only in the young. Stage I nondiploid clear cell carcinomas were associated with death (33%) only in the young. Overall, death rates seem similar for both groups but among the young most (63%) occurred with low-stage disease and a nondiploid pattern only; among the old, 88 percent occurred with high-stage disease and independent of DNA ploidy pattern.