Tumor neoangiogenesis has proven its prognostic value in malignant tumors of different organs including prostatic adenocarcinoma. The aim of this retrospective study was to disclose the significance of neoangiogenesis in incidental prostatic carcinoma (ICP) after transurethral resection (TURP). The authors examined all patients having ICP diagnosed at the Institute of Pathology, Medical Faculty in Ljubljana during the 1985-1989 period, in whom rebiopsy was performed. Ten of 68 patients were examined to determine how microvessels correlate with the degree of tumor differentiation determined histopathologically, and with Gleason score, stage of disease, and survival time. Microvessels were highlighted by immunostaining endothelial cells for factor VIII-related antigen and counted in a x200 microscope field (0.8012 mm2) in the most active areas of neovascularization. Neoangiogenesis and tumor differentiation degree were then correlated between primary tumors and rebiopsies. Tumor differentiation degree was also correlated with the time of the disease progression. Microvessel counts (MVC) showed no association with the degree of tumor differentiation, Gleason score, disease stage, or patients' survival. The time elapsed to the disease progression was associated with less differentiated tumors (p = 0.004; 0.006). Microvessel counts were significantly higher in rebiopsies compared to initial tumors (p = 0.006), but no differences could be observed in the degree of differentiation. The results showed that the determination of microvessel density in rebiopsied patients had a better prognostic value than the degree of tumor differentiation. Nevertheless, the latter showed an association with the time of the disease progression. The number of patients included in the study was too low to confirm the association of MVC and degree of tumor differentiation in primary tumors.