The purpose of this study was to determine the incidence of malnutrition among patients on admission to hospital, to monitor changes in their nutritional status during hospitalization, and to determine the factors which might affect changes in nutritional status. The subjects for the study were patients who were admitted to general medicine for more than one week. Patients suffering from cardiovascular, renal disease, or dehydration were excluded. Nutritional assessment of the patients was performed on admission and nutritional status was reassessed one week and two weeks after admission. The nutritional assessment tool consisted of subjective history taking and anthropometric measurements. Biochemical measurements were performed only on admission. For anthropometric assessment ; patients' body weight, subcutaneous skinfolds thickness, % of body fat, body mass index, and lean body mass were measured using caliper or Bio impedance Analyzer. Factors which might influence current nutritional status, like dietary intake, anorexia, nausea, vomiting, diarrhea, sleep disturbance, and number of day of NPO for diagnostic examinations were analyzed. The results are as follows : 1. Of the 59 patients who were studied, 61% were male and 39% female. The nutritional status of all of the 59 subjects was reassessed one week after admission, but it was only done for 22 subjects at two weeks. 2. The anthropometric measurements, including weight, body mass index, lean body mass, body fat, and skin fold thickness, were all significantly decreased at one week after admission compared to the values at admission. On the other hand, two weeks after admission, only body weight and abdominal skinfolds thickness were decreased. 3. The subjects reported anorexia for an average of two days, sleep disturbance for two days, and no food intake due to diagnostic test for one day. In the second week of hospitalization almost none of the patients complained of gastrointestinal symptoms or sleep disturbance except anorexia Food consumption which was measured based on rice intake was 60% of the food served during the first week of hospitalization, and 66% during the second week of hospitalization. 4. There was no correlation between the subjective nutritional assessment and anthropometric assessment. 5. There was no statistical significance in anthropometric measurements among the patients with various diseases whereas sleep disturbance and no food intake due to various diagnostic test was prominent in patients with gastrointestinal diseases.