Background: Angiogenesis is important in the development of solid tumors. A variety of markers for identification of microvessels in histological sections are available, cluster of differentiation 34 (CD34) is one of the most commonly used factors. Aims: To evaluate the expression of CD34 in invasive squamous cell carcinoma (SCC) and urothelial carcinoma (UC) of the urinary bladder and correlation of its expression with clinicopathological parameters of the patients. Materials and methods: Sixty cases of invasive bladder cancer removed by radical cystectomy were enrolled in this study. The expression of CD34 was evaluated by immunohistochemistry using streptavidin-biotin-technique. Results: CD34 was demonstrated in the cytoplasm and along the cell membrane of endothelial cells in all cases and the mean of microvessel density (MVD) was 69.2 ± 24.38 and 72.7 ± 23.95 in invasive SCC and invasive UC, respectively without a significant statistical difference. Expression of CD34 in invasive SCC was positively associated with tumor grade, pathological T stage and lymphovascular invasion (Kruskal Wallis, p=0.010, Spearman`s rho correlation= 0.389, p=0.034 and Mann-Whitney U, p=0.017 respectively). Invasive UC showed positive correlation with only tumor grade (Mann-Whitney U, p=0.047). Conclusions: MVD as measure of angiogenesis can be used as a prognostic factor in invasive SCC and invasive UC of the urinary bladder. So, angiogenesis inhibitors could be tried as therapeutic adjuvant in decreasing tumor progression. Keywords: Angiogenesis, immunohistochemistry, prognosis, CD34, MVD