Expression of the p53, the epidermal growth factor receptor (EGFr; c-erbB-1) and c-erbB-2 proteins was studied in 82 patients with primary transitional cell carcinoma of the bladder using an immuno-histochemical method. Strong or moderate staining was found in 18% of tumours for p53 with weaker staining in a further 36% giving a total of 54% of tumours stained for p53. Strong staining was found in 15% of tumours for c-erbB-2 and in 31% for the EGFr. Tumours invading the bladder muscle were significantly more likely to be strongly stained positively for p53 and/or EGFr compared with superficial tumours: only 15% of invasive tumours were stained negatively for both p53 and EGFr. No statistical association was found between p53 and EGFr expression. Weakly positive associations were found between the expression of c-erbB-2 and p53 and between muscle invasive tumours and increased expression of c-erbB-2. Alterations in the expression of p53, c-erbB-1 and c-erbB-2 were found frequently in human transitional cell carcinoma of the urinary bladder and may be of clinical use in defining patient sub-groups of differing prognosis.