A randomized trial has compared the results of brush cytology before or after biopsy in patients with solitary gastric lesions. One hundred and eleven carcinomas were identified in 324 patients. False positive histological reports were recorded in 2 patients but there were no false positive cytology results. The cumulative accuracy of biopsy and cytology in patients with carcinoma was 97 per cent, which was significantly better than biopsy alone (83 per cent, P less than 0.001) or cytology alone (87 per cent, P less than 0.001). The cumulative results of brushing before biopsy were significantly better than results obtained by brushing after biopsy (P less than 0.05) and indicate that brush cytology should normally be performed before biopsy.