The specimens used in this study were obtained from patients with primary gastric carcinoma and adjacent non-malignant mucosa from the same patients. Using the techniques of immunocyto chemicstry and in situ hybridization, transforming growth $factor-{alpha}(TGF-{alpha})$ and epiderimal growth factor receptor (EGF-R) nRNAs were identified. $TGF-{alpha}$ was observed in macrophages and dividing tumor cells but, not in normal cells. EGF-R was observed both in malignant and non-malignant gastric tissues. Although normally, $TGF-{alpha}$ is not seen in normal gastric tissues, $TGF-{alpha}$ was discovered in the adjacent non-malignant tissue of histolgically normal, which strongly suggest that $TGF-{alpha}$ is involved in the differentiation of cancer cells. Immunocytochemicstry using EMB-11 antibody identified the existence of macrophages which express $TGF-{alpha}$ and EGF-R mRNA. Protein products of EGF-R was identfified using monoclonal antibody. Cancer cells were also identified in the non-malignant normal tissues by the method of immunocytochemicstry using carcino embryonic antigen (CEA)antibody. It is considered that the activity of $TGF-{alpha}$ increased as tumor cell prolifierates. Immunocytochemistry and in situ hybridization techniques can be used to diagnose gastric cancer along with the use of ${alpha}-feto$ protein and CEA.