The principal objective of this study was to determine the effects of diet knowledge and perception on diet practice behavior among university students. Data were collected between March and April of 2005 from 523 male and female university students in Seoul and Chungbuk, via a self-administered questionnaire. The subjects included 217 male students (41.5%) and 306 female students (58.5%), and 52.0% of the subjects were 21-23 years old. With regard to residence type, 42.6% of the subjects lived in the dormitory, home (29.1%) self-boarding (19.5%) and meal (8.8) were in the order. The average weights and heights of the subjects were as follows: 70.9±9.0 kg and 174.3±4.4 cm in the male students and 53.9±5.9 kg and 161.3±4.5 cm in the female students. The average BMI values of the male and female students were 23.4±2.5 and 20.8±2.1, respectively. The average nutritional knowledge scores were as follows: 1.96 out of 3.0, dietary habit (2.13), nutrition (2.0), exercise (1.98), preferred food (1.90), and chronic disease (1.79). We noted no significant differences between the male and female subjects in terms of scored points. Nutritional knowledge by gender and residence type were shown to be significantly different--the male subjects had higher scores for exercise than did the female subjects. The self-boarding subjects had significantly lower scores with regard to nutritional knowledge and chronic disease. The experience and duration of previous diet practice were also significantly different with regard to gender and residence type. The male subjects tended to conduct diet practice for longer periods than females. The self-boarding students reported more attempts at diet behavior, but for shorter durations. The results show that the nutritional knowledge and diet practice behavior of the subjects were influenced by gender and residence type.