Abstract: Objective To explore the practical means for identifying early large bowel carcinoma and precancerous lesions with magnifying endoscope. Methods We examined 139 patients with polyp using colonoscopy and mucosal staining, and observed the pit patterns (proposed by Kudo) with magnifying endoscope and stereomicroscope to identify the relations between the pit patterns and the pathologic diagnosis. Results Polyps were identified in 124 patients and advanced cancers in 9. Five laterally spreading tumors (LST) ranging from 10 to 50 mm in diameter, including 1 of pit ⅢL, and 4 of pit Ⅳ. were found. The findings of the pit patterns by magnifying endoscope were highly consistent with those by stereomicroscope in these patients. Conclusions Pit patterns are crucial to distinguish the cancerous lesions form non-cancerous one and helpful for early detection of colorectal cancers. Pit Ⅴ may serve as warning sign of early cancerous lesions.