107 bladder tumours cystoscopically suspected to be malignant were examined morphologically by forceps biopsy, aspiration biopsy and exfoliative cytology. The malignancy was graded from 0 through 4. The reproducibility of each method was established, and was found to be 80%, 65% and 90%, respectively. Exfoliative cytology underestimated the malignancy grade as compared with histopathology (59% of the malignant tumours were not jduged as malignant in the cytological grading), but showed no tendency towards overestimation and gave no falsely postiive diagnoses of malignancy. It is concluded that diagnosis of bladder tumours requires both biopsy and cytological techniques, since they proved complementary in a number of cases. Grading by aspiration biopsy is less reliable but may be of benefit in selected cases where forceps biopsy is less suitable.