Immunohistochemical staining of urothelial tumours using paraffin-embedded tissue blocks was performed for p53 and Retinoblastoma (RB) proteins, to characterize any correlation with sensitivity to hyperthermia treatment. Seventeen patients with primary urothelial tumours (16 of the bladder and one of the ureter) treated at our institute between July, 1987 and March, 1993 were included in this study; tissues investigated consisted of 16 transitional cell carcinomas (TCC) (6 Grade2 (G2), 6 G3, 2 G2 > G3, 1 G3 > squamous cell carcinoma (SCC), 1 undifferentiated carcinoma > G3), and 1 SCC. One case was Tis, 4, 3, 1, and 4, were T1 to T4, respectively, and 4 were post-cystectomy. Clinically, in terms of response to treatment, there were four complete response (CR) cases, four partial response (PR) cases, six no change (NC) cases, and three progressive disease (PD) cases, the total in which treatment was effective thus accounting for approximately half of those examined (CR + PR, 47%). Immunohistochemically, six of eight pre-hyperthermia lesions which demonstrated positive staining for RB were CRs or PRs, 75% of which were high-grade lesions, and 50% exhibited invasion and lymph node metastasis. Only three in total were positive for p53 staining, two of which were T4 and these both responded to treatment. The results suggested that RB gene expression may be related to heat sensitivity to some degree.