Gastric cancer (GC) is a frequent neoplasm with high mortality. Most patients in occidental countries show advanced stages of the disease, and low resectability rates. In this paper, some epidemiological items are detailed. The morphologic classifications, TNM stages and risk factors for GC are defined. Clinical manifestations are described, focused in the necessity of early diagnosis as it is the only way to reduce mortality. The usefulness of diagnostic methods in preoperative staging are discussed in relation to the role of these methods in the prediction of resectability and the evaluation of new therapeutic regimens. The role of radical surgery and extended lymphadenectomy as definitive treatment is analyzed as well the role of adjuvant and palliative interventions. The experience in Instituto Nacional de Cancerología is briefly described.