Transforming growth factor-beta 1 (TGF-beta 1) is a pleiotrophic growth factor in carcinogenesis and regulars multiple cell functions. We wanted to evaluate the diagnostic meaning of TGF-beta 1 plasma levels in patients with a biopsy proven prostate cancer. The TGF-beta 1 blood level was analysed in 394 patients. In 242 patients (group I) the blood was taken before any prostate manipulation and biopsy. The TGF-beta 1 plasma concentrations were almost similar in the group of patients with a prostate cancer (n = 157) and patients with a benign prostate hyperplasia (n = 85; 14,258 pg/ml versus 14,658 pg/ml, SD 10,516 pg/ml). In 152 patients the blood was taken 6-12 months after radical prostatectomy (group II). There was no significant difference between the patients with a PSA-progress and without PSA-progress after. Our results suggest that TGF-beta 1 plasma levels can not be used to distinguish between patients with prostate cancer and benign prostate hyperplasia.