We reviewed the diagnostic process in 6 minute, 6 small and 9 flat early cancers detected preoperatively, and in additional 12 flat cancers that were found in resected stomachs only at histology between 1976 and 1986. The limit of the size of cancer detectable preoperatively was 4 mm. Endoscopically, 7 out of 12 minute and small cancers detected preoperatively showed obvious morphological changes, while the others showed only color changes with or without erosion. Lesions with morphological changes significantly invaded the mucosa more often than those with no such changes (p = 0.010). Among flat cancers, color change was significantly more frequently observed in cancers involving the whole mucosa than in those confined to the superficial part of the mucosa (p = 0.015). Redness and discoloration were significantly more frequent in the differentiated and undifferentiated groups, respectively (p = 0.005). This study suggests that morphological and color changes are important indicators of minute or small cancers, especially those involving the whole mucosa.