Differential diagnosis of epithelial tissues of normal human gastric,undifferentiated gastric adenocarcinoma,gastric squamous cell carcinomas,and poorly differentiated gastric adenocarcinoma were studied using the mean diffuse reflectance spectral ratio (R540/R575) of the oxygenated hemoglobin absorption bands. Exvivo diffuse reflectance spectra in the 400 nm to 600nm region was measured from surgically removed gastric lesions using a spectrophotometer with an integrating sphere attachment. The results showed that the reflectance spectral intensity of the malignant tissues was lower than that of human normal gastric tissues and showed dips at 540 nm and 575 nm owing to absorption from oxygenated hemoglobin. Measurements carried out,the diffuse reflectance spectral ratio for epithelial tissues of normal human gastric,undifferentiated gastric adenocarcinoma,gastric squamous cell carcinomas,and poorly differentiated gastric adenocarcinoma were (94.2±2.4)%,(109±3.0)%,(103±2.8)% and (98.6±2.6)% respectively.