In 135 renal cell carcinomas (RCCs), nuclear grade, Robson stage and DNA content, determined by flow cytometry, were related to the 3-year survival rates of the respective patients. All three parameters showed prognostic value, nuclear grading being most effective. Combined evaluation of the parameters showed that staging and also DNA determination add supplementary prognostic information. As the four nuclear grades clearly uncover the biological potential of RCC, they are regarded as the most significant criteria for the prognostic assessment of RCC.