Malnutrition is one of the most important factors for the development of nosocomial infection (NI). We performed a study of the correlation between abnormal nutritional factors and NI risk by investigating the patients who stayed longer than 3 days in the intensive care unit (ICU) of our university hospital. The patients were classified into three groups based on serum albumin levels and total lymphocyte counts (TLC). The criteria of Group I (well nourished group) were serum albumin level of 3.5 g/dl or higher and TLC of 1, 400/mm³ or higher. The criteria of Group III (severely malnourished group) were serum albumin of less than 2.8 g/dl and TLC of less than 1, 000/mm³. The other patients were classified as Group II (moderately malnourished group). The occurrences of NI were monitored during the study period and the APACHE III Score was calculated. The probability of first NI infection in Group III was 2.4 times higher than that in Groups I & II. The mortality rate of 20.5% was more significantly correlated with APACHE III Score than nutritional status. Nineteen (53%) of the total 36 NI patients were infected within 10 days after ICU admission and they all belonged to Group III. When we compared the gap period between infections, the time to first infection was significant.