Introduction: The expression pattern of cyclins D1 and E, as well as cyclin-dependent kinase inhibitors p21(Wa1/Cip1) and p27(Kip1) and their relationship to tumour behaviour and patients’ prognosis was examined in 142 urothelial cell carcinomas. The expression of these proteins was also analyzed along with other cell-cycle-related proteins such as: p53, pRb and the proliferation-associated indices Ki-67 and proliferating cell nuclear antigen (PCNA). Patients and Methods: These molecule markers were localized immunochemically using the monoclonal antibodies anti-cyclin D1 (DCS-6), anti-cyclin E (13A3), anti-p21 (4D10), and anti-p27 (1B4) in 142 patients with urothelial cell carcinoma. Results: Focal positivity (<10% of tumour cells) or the absence of cyclin D1 immunostaining was observed in 105/142 (73.9%) of the tumours. Cyclin D1 expression was correlated with tumour grade and stage as well as with the existence of in situ component. In addition, cyclin D1 expression was positively correlated with p21(Waf1/Cip1) and p27(Kip1) and inversely with the Ki-67 score. Focal positivity (<20% of tumour cells) or the absence of cyclin E immunoreactivity was observed in 105/142 (73.9%) in all cases. Cyclin E expression was correlated with tumour stage. A positive relationship between cyclin E expression and the two associated proliferating indices Ki-67 and PCNA, as well as with p53 and p27(Kip1) proteins expression was noted. Absence or focal positivity (<5% of tumour cells) of p21(Waf1/Cip1) was detected in 88/142 (62%) of the carcinomas. p21(Waf1/Cip1) expression was correlated with tumour grade and stage. A positive relationship of its expression cyclin D1, cyclin E, p27 and pRb expression was observed. Absence or focal immunostaining (<20% of tumour cells) of p27 protein was detected in 55/141 (39%) in all cases. p27(Kip1) expression was correlated with tumour grade as well as with cyclins D1 and E. The prognostic significance of cyclins D1, E and cyclin-dependent kinase inhibitors p21(Waf1/Cip1), p27(Kip1) in determining the risk of recurrence and progression with both univariate (log rank test) and multivariate (Cox regression) methods of analysis showed no statistically significance differences. Conclusion: These findings suggest that the level of the cell cycle regulators studied does not seem to have a clinical value in terms of predicting the risk of early recurrence and progression. In addition the interrelationship probably means their contribution to the regulation of cell growth through different pathways in bladder carcinogenesis.