The purpose of this study was to investigate the effect of nutritional education on the knowledge and the practice & Perception of diet therapy, and on the level of FBG and HBAlc. The subjects were selected among the patients treated in the Inha University Hospital from June of 1996 until April of 1998. Educated group consisted of 20 patients who visited the diet-counseling department as a part of diabetic treatment. Non-educated group consisted of 20 patients who visited the diet-counseling department ignoring doctors prescription purpose. The knowledge and the practice & perception of diet therapy drinking & smoking habits, regular exercise, and general characteristics including family history were analyzed by questionnaires. FBG and HbAlc were measured before and 4 months after the treatment. The results were as follows : Both groups were composed of 12(60%) male and 8(40%) female respectively. The mean age of subjects was 51.4 years in educated group and 51.9 tears in non-educated group. The duration and %IBW were 5.9 years and 109.8 % in educated group and 5.5 years and 111% non-educated group respectively. There were no significant differences in drinking & smoking habits and regular exercise between groups. The diet therapy knowledge score was significantly higher in educated group(p<0.001, 5.8$pm$2.3/10.0 vs 3.4$pm$2.0/10.0). The diet therapy practice & perception score was also significantly higher in educated group(p<0.001, 5.6$pm$2.3/10.0 vs 2.8$pm$2.2/10.0). Levels of FBG and HbAlc in both group were reduced at 4 month after the treatment(-74.2 mg/dl and -1.4% in educated group vs -58.7 mg/dl and -2.0% in non-educated group). However, the reduced amounts of them were not significantly different. Therefore, nutritional education seems to be very important in improving the knowledge and the practice & perception of the diet therapy. However, it appears no direct influence in reducing FBG and HbAlc levels. Further studies on diabetic management by using more efficient, consecutive and intensive nutritional education methods are needed. (Korean J Nutrition 34(1):69-78, 2001)