Evaluation of cell cycle regulators has gained special interest in the effort to increase the amount of prognostic information in malignant tumors. Minichromosome maintenance proteins (MCMs) drive the formation of prereplicative complexes, which is the first key event during G1 phase. Therefore, altered MCM expression may be a hallmark of cell cycle deregulation, which is supposed to be the most essential mechanism in the development and progression of bladder cancer. Our aim was to investigate the value of MCMs as proliferation markers and prognostic indicators in detrusor muscle-invasive urothelial bladder carcinomas. We analyzed immunohistochemically the expression of MCM-2 and MCM-5 in 65 patients with detrusor muscle-invasive urothelial bladder carcinomas in relation with clinicopathologic parameters, patients' overall and disease-free survival, and the expression of the conventional proliferation index Ki-67 and other cell cycle modulators (p53, pRb, p21(WAF1), and p27(Kip1)). The levels of MCM-2 and MCM-5 were significantly higher in high-grade (P < .0001), advanced-stage (P = .001), and nonpapillary tumors (P < .0001). The expression of MCM-2 and MCM-5 significantly associated with the conventional proliferation index Ki-67 (P = .0001 for each protein). The expression of MCM-2 or MCM-5 positively correlated with p53 labeling index (P = .014 and P = .009, respectively). Also, median p21(WAF1) labeling index was higher in MCM-5 high expressors (P = .028). Finally, both MCM-2 and MCM-5 associated significantly with adverse patients' outcome in both univariate (P = .0072 and P = .0074, respectively) and multivariate (P = .0001) analysis. In conclusion, MCM-2 and MCM-5 appear to be reliable proliferation indexes and useful prognostic markers in patients with muscle-invasive urothelial bladder carcinomas.