This study was performed to develop an index assessing the overall diet quality for Korean. The study subjects consisted of preschool children (PC), elementary school children (EC), high school students (HS), college students (CS), and adults over 30 years old living Seoul and the surrounding areas. The subjects over 30 years old were classified to 30-49 years, 50-69 years, and over 70 years. A dietary survey was conducted using 24-hour recall method and data were collected from 2392 people. Newly developed Korean diet quality index (KDQI) was an index assessing the overall diet quality from the view point of balance. KDQI was based on the nutritional problems of Koreans, dietary risk factors for chronic degenerative diseases, 5 major food groups, and dietary guidelines. The ten components of KDQI were vegetables, fruits, dairy products, dietary variety score, calcium intake, iron intake, energy intake, fat intake, and cholesterol intake. The full score of each component was 10 points and the score of KDQI was calculated by summing the scores of the 10 components. When the KDQI was applied to this study subjects, the distribution of subjects KDQI scores was similar to normal distribution. Mean score of KDQI was 56.0 and the range of the mean by age was from 45.7 for the subjects over 70 years old to 60.7 for the elementary school children. The components which composed the lowest three means were dairy intake, fruit intake, Ca intake in most age groups. Mean score of DVS was one of the highest three but not for the subjects over 50 years old. After subjects with KDQI score over 70 were classified to higher poop and those with KDQI score under 40, to lower group, nutritional characteristics were compared. Energy contributions of carbohydrate, proteins, and fit, percentages of RDA for major nutrients, and dietary diversity scores were more adequate in the higher poop than in the lower group. The lower poop had more risks for chronic degenerative diseases. According to the results, KDQI was valid index to assess the overall diet quality and it could be used to detect risk group for malnutrition and chronic degenerative diseases.