The distribution of S-100 protein positive dendritic cells (S100-DCs) in cancer nests and the expression of HLA-DR antigen on cancer cells in 90 patients with transitional cell carcinoma of the urinary bladder were studied immunohistochemically. A dense infiltrate of S100-DCs (more than 10 S100-DCs/high power field) was detected in 47 out of 90 cases, while in the remaining tumours the infiltrate was sparse. HLA-DR positive cancer cells (DR-CCs) were detected in 24 cases, including 16 with dense DR-CCs (more than 100 DR-CCs/high power field); no expression was observed in the remaining tumours. In terms of the numbers of S100-DCs infiltrating the following statistically significant differences were observed: tumour grading G1 > G3, depth of penetration pT0 > pT3; (p < 0.05), G2 > G3, lymphatic invasion – > + and venous invasion – > +; (p < 0.01). A multivariate analysis demonstrated that the most important factor affecting prognosis was distant organ and/or lymph node metastasis (p < 0.01) the number of S100-DCs, with a hazard ratio (HR) of 0.26 (p < 0.01), and the number of DR-CCs with HR of 0.18 (p < 0.05); these were statistically significant. S100-DCs and DR-CCs may be regarded as independent prognostic factors of tumour growth and progression.