There were studied 84 patients with benign and malignant hypertrophia of the prostate from a cytomorphological point of view. Fine needle aspiration and transurethral resection was practised and a comparison between cytologic and histologic results was made. There were 14 adenomas, 3 adenomas with associated atypic canalicular hyperplasia, 6 adenomas with associated carcinoma and 61 carcinomas. Cytologic observations revealed malignant cells in 59 from 61 cases of carcinoma and in 4 from 6 adenomas with carcinoma. General accuracy of the method was appreciated at 96.8%. The incidence, causes and significance of false negative and one false positive results are discussed. Using Gaeta system as standard for histologic grading we may conclude that information (as well as histological form of the tumor and invasion) is difficult or even impossible to obtain only by the study of the smears. The importance of the method for detection of "early cancer", its inocuity, repeatability and the reduced number of complications recommend it as the most useful in the diagnosis of prostate carcinoma.