A combined evaluation effort of the Boehringer Mannheim Research and Development and Evaluation Departments and the University Hospital Rotterdam is described regarding the new, fully automated Enzymun-Test PSA assay for prostate-specific antigen. The study consisted of an analytical and a clinical part. At both sites, the vast majority of intra-assay coefficients of variation ranged from 2 to 3% above prostate-specific antigen = 1 microgram/l. Below that concentration higher coefficients of variation were measured. Comparable results were obtained for the interassay imprecision. The analytical sensitivity (lower limit of detection) was found to be 0.02 microgram/l at both sites. Regarding the linearity of the assay no systematic drift to either elevated or lower values which increasing dilution was found. Deviations remained well in the range between 100 +/- 10%. The correlation with the Abbot IMx PSA assay as performed with a large set of clinical specimens revealed: y (= Enzymun) = 1.16x (= IMx) + 0.0; r = 0.985; n = 245. In this comparison study small differences between benign prostatic hyperplasia patients and prostate cancer patients were detected, perhaps partly based on the differences in recognition patterns of various molecular prostate-specific antigen forms in both assays. A follow-up after radical prostatectomy with 17 patients (50 serum samples) also showed a good comparability between the Enzymun-Test and the IMx assay. The limited check of the reference range resulted in data comparable to what can be found in the literature: out of 100 samples originating from healthy males, aged 20-60 years, 99 had prostate-specific antigen values lower than 4 micrograms/l. Based on our findings it can be concluded that the new Enzymun-Test PSA assay meets the current state-of-the-art criteria in prostate-specific antigen methodology.