Weight loss and malnutrition are common in cancer patients. Although weight loss is predominantly due to loss of fat mass, the morbidity risk is given by the decrease in muscle mass. The assessment of nutritional status is essential for a diagnosis of nutritional compromise and required for the multidisciplinary approach. Subjective global assessment (SGA) is made by the patients nutritional symptoms and weight loss. The objective assessment, a significant weight loss (>10%) for 6 months is considered an indicator of nutritional deficiency. The mean body index, body fat mass and body protein mass are decreased as cancer stage increases. The biochemical data of albumin, cholesterol, triglyceride, Zn, transferrin, total lymphocyte count are decreased in advanced cancer stage. Daily energy intake, cabohyderate and Vit B1 intake is decreased according to cancer stage. The patients are divided into three groups according to SGA. The three groups showed a significant difference in body weight, 1 month weight loss%, 6 month weight loss%, body mass index, mid arm circumference, albumin, energy intake, as well as carbohyderate intake protein and energy malnutrition. Nutritional assessment is of great importance because undernutrition has been shown to be associated with increase in stomach cancer associated morbidity and mortality. The authors concluded that nutritional assessment should be done in cancer patients preoperatively, and with adequate nutritional support, the morbidity and mortality would be decreased.