The diagnostic value of endoscopic biopsy from the ulcer margin (six specimens) and the base (six specimens) in 46 cases of gastric malignancy was evaluated. The biopsy positive rates for malignancy from the ulcer margin and the base were 42 of 46 (91.3%) and 37 of 46 (80.4%), respectively (P = 0.2312). The diagnostic positive rate was increased to 95.6% (44 of 46) when the results of 12 biopsy specimens obtained from the ulcer margin and the base were combined. The diagnostic positive rate was not statistically different when the morphology or the location of the gastric malignancy was considered. No complication of massive bleeding or perforation was found after both sites had been biopsied. It is concluded that the margin and the base of a gastric malignant ulcer are both suitable and diagnostically effective for endoscopic biopsy. If the ulcer margin of the gastric malignancy is difficult to approach, the ulcer base appears to be a satisfactory alternative site for endoscopic biopsy.