Tumour angiogenesis is widely considered to be an important phenomenon in the process of tumour growth and metastasis. We investigated the prognostic significance of the microvascular count (MVC) in prostate cancer of each Gleason grade and compared the results to other established pathologic parameters and progression probability. We also compared the staining of Factor VIII-related antigen (FVIII-RA) with CD34 antigen (CD34 Ag) staining for determination of the MVC. We examined 101 radical prostatectomy specimens from patients who underwent curative therapy for clinically localized adenocarcinoma of the prostate as the first form of therapy. To identify microvessels, immunohistochemical staining of endothelial cells was performed using antibodies to FVIII-RA and CD34 Ag in formalin-fixed, paraffin-embedded tissue. Microvessels were counted in fivex200 fields (0.785 mm(2) on each Gleason grade in the 'hot' areas. We used the highest number of five fields in the worst Gleason grade on each staining for statistical analysis. MVC using FVIII-RA and CD34 Ag staining correlated with pathologic stage, Gleason score and preoperative serum prostate-specific antigen level. In addition, MVC using CD34 Ag staining also correlated with DNA ploidy and total tumour volume. The Gleason score was found to be the best prognostic indicator using Cox proportional hazards regression analysis. In this study, MVC in prostate cancer was predictive of pathologic stage and Gleason grade, but MVC by either FVIII-RA and CD34 Ag staining was not an independent prognostic predictor. The best prognostic indicator in this study was Gleason score.