胃癌是目前世界第二位最常見癌症及第二位癌症死因，具有相當大的地區別變異及遷徙效應。世界各國包括台灣之胃癌死亡率皆呈下降趨勢，而且胃癌在台灣地區也是重要癌症，死亡率隨年齡的增加而上升，1994年胃癌的發生率和死亡率分別位居全國十大癌症的第六位和第三位。臨床上胃癌可分為早期胃癌及進行性胃癌，其五年存活率分別為90%及10%。和胃癌有關的環境因子包括蔬菜、水果、維生素A和E、胡蘿蔔素、硒、醃製或鹽漬食物的攝食，抽菸酗酒，幽門螺旋桿菌感染，電冰箱的使用及社經地位。胃癌有關的基因研究包括一等親胃癌家族史，麩胺基硫轉移酵素M1基因 多形性。胃癌的多因子多步驟致病機轉，可能包括正常胃組織經幽門螺旋桿菌的感染而發生表面胃炎，而後受到鈉鹽的刺激，進一步造成萎縮性胃炎，此時胃內部環境若是高pH值、有細菌生長以及亞硝胺致突變物的作用，可能導致腸性化生，再經異生而導致胃癌。

　　　　　Gastric cancer is the second common cancer in the world with striking geographical variation and migrant difference in spite of its declining secular trend in nearly all countries including Taiwan, where the incidence and mortality of gastric cancer still ranked as sixth and third leading cancer site, respectively, in 1994. Early gastric cancer and advanced gastric cancer have different 5-year survival rates of 90% and 10%, respectively. The investigation of risk factors for gastric cancer is essential f or effective prevention and early detection of gastric cancer. The environmental risk factors of gastric cancer include low intake of vegetable, fruit, vitamin A and E, carotenes, and selenium, high intake of salty food, cigarette smoking, habitual alcohol consumption, Helicobacter pylori infection, and low socioeconomical status. Genetic components including family aggregation and glutathione S-transferase M1 null genotype have been documented as risk factors for gastric cancer, but their roles in gastr ic carcinogenesis remains controversial and needs further elucidation. A multistep and multifactorial process of human gastric carcinogenesis was suggested. Excessive salt intake and infection with Helicobacter pylori play important roles on the initial stages of gastritis and atrophy, and b-carotene and excessive salt intake on the final stages with a sequence of intestinal metaplasia, dysplasia, and carcinoma.