The diagnosis and histological characterization of undifferentiated and advanced carcinoma of the prostate gland is fairly well established and generally recognized. A relatively significant number of cases remain however, in which the objective recognition of carcinoma of prostate is controversial. Similarly, precancerous changes occurring in atrophy and hyperplasia are not generally fully recognized. A comprehensive approach will be made with the application of Scanning Electron Microscopy, Histology and Cytology to formulate a set of useful criteria for the characterization and recognition of such lesions. To establish a baseline, a sufficient number of samples will be obtained to include the full spectrum of prostate disease. However, the main emphasis will be the study and characterization of borderline cases. Adequate biopsy, surgical and postmortem material will be selected for formalin, frozen and acetone fixation. Additional material will be obtained from the Prostatic Cancer Tissue Collection Center, University of Miami School of Medicine, if and when necessary to cover the entire spectrum of prostatic disease.