The main objective was to evaluate a patient's immunologic and nutritional status as a prognostic indicator of morbidity and mortality in patients with gastric cancer. A prospective clinical study carried out at the National Cancer Institute in Bogotá, Colombia. Our study group consisted of 40 patients with a diagnosis of gastric adenocarcinoma that was treated surgically. Blood samples were taken before and 5 d after surgery; mononuclear cell typing was done by flow cytometry allowing a bicolor analysis. Nutritional evaluation was obtained through measurement of albumin levels, average weight loss, and nutritional risk index (NRI). Half of the malignancies were localized to the middle and lower third of the stomach: stage I, 17.55%; stage II, 10%; stage III, 55%; and stage IV, 17.5%. Twenty subtotal gastrectomies, 11 total gastrectomies, 7 gastrojejunostomies, and 2 esophagogastrectomies with D1 and D2-D3 lymph node resection were performed. A postoperative morbidity of 22.5% and a mortality of 7.5% were observed. A preoperative cellular immunosuppression was identified, with a helper lymphocyte (CD4) to suppressor/cytotoxic lymphocyte (CD8) ratio of 1.38 normal value (NV > 1.5), which increased according to the stage of the disease. Patients who died presented with a significantly greater preoperative cellular immunosuppression than those who survived (P = 0.05). Postoperative mortality correlated significantly with hypoalbuminemia (P = 0.008). In those who died, weight loss was greater than in those who survived (P = 0.06). Patients with severe malnutrition had greater postoperative mortality according to the NRI. Severe preoperative cellular immunosuppression (CD4/CD8 < 1), hypoalbuminemia, weight loss, and severe NRI have a positive predictive value for mortality in patients with gastric cancer.