Cellular material, considered sufficient for reliable cytological interpretation, was obtained by prostatic massage from 306 male patients. The strictly cytological results, ranging from class 1 (normal) to class 5 (conclusively positive for carcinoma), were then compared with the combined results of all other available clinical, roentgenographic, and laboratory findings. A false-positive diagnosis of carcinoma occurred only once. In the assembled data of the authors and of previous investigators, false-negative cytodiagnoses have occurred 55 times in 324 cases. Some hard, frankly malignant glands yield insufficient secretion. The authors believe that palpation remains the best means for diagnosing prostatic carcinoma in its early asymptomatic stages, but cytodiagnosis, yielding few false-positive results, is of great corroborative value in the diagnosis of inoperable prostatic cancer.