Fine needle aspiration biopsy cytology allows safe morphologic tumor diagnosis in the prostate based on cytologic and histologic criteria. Specific technical difficulties of the procedure are not greater than in surgical pathology. The standardized equipment developed by FRANZEN is recommended. Aspiration biopsy is atraumatic and without complications. The method introduces a new clinical approach to the application of recent advances in cell research. Among other improvements, aspiration biopsy may falicitate cytologic classification of prostate carcinoma. The method should be adapted to screening programs.