The historical development of different techniques for the study of proliferative patterns of normal and malignant tissue is explained. For more than 100 years, pathologists and clinicians have attempted to clarify the prognostic impact of this tumor-biological parameter. One relevant result of these investigations is the ‘Grading-System’, a histomorphological description of tumor cell differentiation. The auto-radiographic method using tritiated thymidine (thymidine incorporation assay) detects a portion of DNA-sythesizing cells directly. However, radioactivity and long autoradiographic exposure times are the main disadvantages. DNA cytophotometry and immunohistochemical labeling are currently the most frequently used techniques for direct assessment of proliferating cells in normal and malignant renal tissue as well as in other human tumor tissues. Concerning renal cell carcinoma (RCC), our own experience and the results of the literature are compared and discussed: In contrast to tumor staging, tumor grading correlates with the tumor-specific proliferation rates. According to the present data, the measurement of the proliferative kinetics seems to be a relevant prognostic parameter for detection of high-risk patients, especially in the early stages showing identical histological findings for staging and grad