Morphometric nuclear parameters were compared with patient survival for a series of 174 renal cell carcinomas (RCC) collected over a 30 yr period. Stepdown regression showed long diameter, average feret diameter, form factor and the ratio of average feret diameter to equivalent diameter to be significantly associated with survival. Nuclear area, nuclear perimeter, equivalent diameter, ratio of long diameter to average feret diameter and coefficients of variation of nuclear area and nuclear perimeter were not significantly correlated with survival. All parameters were correlated with a 3 division nuclear grading classification using analysis of variance. Multivariate analysis showed nuclear form factor, tumor stage, silver staining nucleolar organizer region numbers and proliferating cell nuclear antigen expression to be independently associated with survival. The results of this study indicate that form factor is the most discriminate morphometric parameter for RCC, providing survival data additional to that derived from tumor staging and from markers of tumor proliferation.