Underweight patients were studied with respect to changes in their nutritional status before and after administration of nutritional beverage. Patients with renal hepatic or endocrine disease gastrectomy malabsorption and weight gain over past 6 months were excluded. Ten patients were participated as controls and were allowed to eat ad libitu, Twenty patients were served as case and were administered in addition to their usual diet 400ml of nutritio-nal beverage(Greenbia) high in calorie and protein for 8 weeks. In the beginning of the study most underweight patients showed depressed nutritional status in terms of calorie intake quality of protein intake and the levels of visceral protein status and serum micronut-rients. The controls consumed less amounts of calories proteins vitamins and minerals while those given the nutritional beverage exceeded their estimated energy requirement(105%) and consumed a mean of 96g protein per day. Those given nutritional beverage for 8 weeks showed significant increase in body weight(3%) hemoglobin(3.2%) hematocrit(5.4%) serum transferrin(19.4%) iron(30.1%) and zinc(20.9%) In the controls however significant improvement was not observed in any parameters compared with initial values. significant improvement was not observed in any parameters compared with initial values. This study suggests that patients with underweight can show mild nutritional deprivation nutritional support can improve their unbalanced status and prevent severe malnutrition.