To establish the earliest sign of stomach cancer in endoscopy and to reveal the subsequent morphologic changes of the lesion, we studied retrospectively 41 cases of stomach cancer. The eariest sign consisted of redness, small polypoid lesions, flat mucosa with slight unevenness and small depressed lesions. There was no clear correlation between the observation period and the size of cancer lesion in cases of early stomach cancer. In cases of advanced cancer, however, the observation period correlated with the size of cancer lesion to a certain extent, and the correlation between the area of cancer (Y cm2) and the observation period (X months) gave a linear equation of Y = 0.68X-3.13.