Immunoreactivity of p21WAF1/CIP1 and cyclin D1 proteins was assessed in a cohort of 207 patients with superficial (pTa-pT1) bladder cancer followed up for a mean of 4.9 years. The results of the immunostainings were compared with T category, WHO grade, tumor cell proliferation rate (MIB-1 score), the expressions of p53 and bcl-2 as well as survival. Sixty-eight percent and 75% of the tumors were p21WAF1/CIP1 positive (> or = 5% of cells positive) and cyclin D1 positive (> or = 10% of cells positive), respectively. The p21WAF1/CIP1 expression was related to cyclin D1 immunolabelling (P < 0.001) but not to the other variables studied. The expression of cyclin D1 was inversely associated with T category (P = 0.001), WHO grade (P = 0.006), MIB-1 score (P = 0.014), p53 expression (P = 0.001), and bcl-2 (P = 0.011) immunoreactivity. In univariate analysis, T category (P = 0.0001), WHO grade (P < 0.0001), MIB-1 score (P < 0.0001), bcl-2 (P = 0.0092), p53 (P = 0.0016) and p21WAF1/CIP1 (P = 0.009) expressions were significant prognostic factors with regard to tumor progression, whereas cyclin D1 was without any prognostic significance (P = 0.1). Out of 123 p21 positive tumors 21 progressed, whereas only 2 out of 58 p21 negative tumors progressed. In multivariate analysis, the MIB-1 score was the only independent predictor of cancer-specific survival (P = 0.03), whereas tumor grade (P = 0.002) and cyclin D1 expression (P = 0.04) were independent predictors of tumor recurrence. Only the WHO grade (P = 0.04) retained its prognostic value indicating the risk of progression. We suggest that in superficial bladder cancer p21WAF1/CIP1 and cyclin D1 immunohistochemistry provide no additional prognostic information compared with already established prognostic factors for predicting the risk of progressive disease.