In an effort to identify enzymatic activities in primary prostatic carcinomas that might be complementary to histological and other clinical techniques for the prediction of prognosis, we have assayed several enzymatic activities extracted from prostatic carcinomas. We reported previously that, for each of the studied enzymes, tissues with benign prostatic hyperplasia and prostatic carcinoma showed significantly different activities. With additional patients now included and a longer interval since resection of these tumors, we have found that the histological grade (Gleasons system for grading) of the sample (prostate chip) analyzed is related to several activities extracted from the cancers including arginase (r = -0.81, p < 0.0001), glucose-6-phosphate dehydrogenase (r = 0.72, p < 0.0001), and the B isoenzyme of N-acetyl-β -D-glucosaminidase (r = -0.58, p = 0.0369). Acid phosphatase (r = 0.15, p = 0.5530) and the BB isoenzyme of creatine kinase (r = -0.13, p = 0.5221) are not significantly related to histological grade. In a large series, Gleason grade is related to survival. In our series of 27 patients followed for 20 to 46 months, the Gleason grade (p = 0.22) is not related to survival, but arginase activity is related (p = 0.0392) to survival. In this small series, arginase is more valuable than the best currently proven predictor of survival, Gleason grade. Hexosaminidase B activity approaches being significantly (p = 0.0575) related to survival. Of the 11 patients whose tumors contained the lowest arginase activities, eight are dead. Of the 11 with the highest activities, only one is dead. Several of the enzyme activities in this series of 27 patients complemented each other for the prediction of Gleason grade; for example, glucose-6-phosphate dehydrogenase, arginase, and the BB isoenzyme of creatine kinase were more closely correlated (multiple correlation coefficient, r = 0.77) with the Gleason grade for all chips than was any single enzyme: arginase, r = -0.67; glucose-6-phosphate dehydrogenase, r = 0.67; creatine kinase, r = -0.16. It seems likely that enzymatic analysis may provide an approach that is qualitatively different from and complementary to histological evaluation for the prediction of prognosis in prostatic carcinoma. Verification of this hypothesis will require more patients followed over a longer period of time and will probably be facilitated by analysis of several samples from different locations in each tumor. © 1985, American Association for Cancer Research. All rights reserved.