The aim in this study was to estimate and compare the zinc levels in paired non malignant and malignant tissues obtained from patients diagnosed with stomach or colon cancer. His-tological normal and neoplastic human gastric or colon tissues obtained from the same indi-vidual at the time of surgery were excised and analyzed for tissue zinc. A significant de-crease in tissue zinc was observed in the tumor tissue as compared with the non cancerous tissue of the same patients. The mean tissue zinc level in the malignant tissue of the stomach showed a 68% significant decrease as compared with the non cancerous tissue of the same individuals. The maximum % decrease in tissue zinc from the normal tissue was observed in poorly differentiated carcinoma as compared with moderately and well differentiated carci-noma. In colon cancer, the mean tissue zinc level was significantly decreased (66%) in the malignant tissue as compared with the non cancerous tissue of the same patients. This study suggests that there is an inverse association between the tissue zinc levels and the advanced stage of carcinoma of the stomach or the colon.