Quadrant biopsies of normal-looking mucosa were used as part of the assessment of cases with superficial Ta,T1 transitional cell cancer of the bladder. Patients with one or more abnormal biopsies were shown to have a significantly greater chance of developing recurrent tumour compared to patients with normal mucosal biopsy findings. Other factors noted at the time of initial assessment, such as size, number of tumours, Ta,T1 category or grade of tumour did not predict recurrence, although recurrences that invaded muscle were associated with G3 histology in the primary tumour. The results of mucosal biopsy identified patients at risk for recurrence and it is possible that this group would derive particular benefit from adjuvant chemotherapy.