101 gastrobioptic series from 93 consecutive patients with a final diagnosis of carcinoma of the stomach were reviewed. 20 false negative cases were found. Of these, ten cases were missed because of erroneous histopathological interpretation, two because of too few sections, and eight because carcinoma was not represented in the biopsies. The frequency of false negatives was slightly larger in ulcerating carcinomas than in polypoid and diffusely spreading carcinomas, mainly due to seven cases of ulcerating carcinoma being missed by the pathologist. There was no correlation between false negatives and histological type. The rate of false negatives was significantly higher in cases, where the number of biopsies taken was below seven. The rate of histopathological misinterpretations was significantly higher in cases, where the number of actually positive biopsies was below four. Attempts to increase the positive yield should be based on not only an evaluation of the biopsy technique, but also an analysis of the histopathological method and interpretation.