Background: The food supply and dietary preferences have changed in recent decades. Objective: We studied time- and age-related individual and population- wide changes in a dietary quality score and food groups during 1985-2006. Design: The Coronary Artery Risk Development in Young Adults (CARDIA) study of 5115 black and white men and women [aged 18-30 y at year 0 (1985-1986)] assessed diet at examinations at study years 0, 7 (1992-1993), and 20 (2005-2006). The dietary quality score, which was validated by its inverse association with cardiovascular disease risk, summed 46 food groups rated by investigators as positive or negative on the basis of hypothesized health effects. We used repeated-measures regression to estimate timespecific mean diet scores and servings per day of food groups. Results: In 2652 participants with all 3 diet assessments, the mean (±SD) dietary quality score increased from 64.1 ± 13.0 at year 0 to 71.1 ± 12.6 at year 20, which was mostly attributable to increased age. However, the secular trend, which was estimated from differences of dietary quality scores across time at a fixed age (agematched time trend) decreased. The diet score was higher in whites than in blacks and in women than in men and increased with education, but demographic gaps in the score narrowed over 20 y. There tended to be increases in positively rated food groups and decreases in negatively rated food groups, which were generally similar in direction across demographic groups. Conclusions: The CARDIA study showed many age-related, desirable changes in food intake over 20 y of observation, despite a secular trend toward a lower diet quality. Nevertheless, demographic disparities in diet persist. © 2012 American Society for Nutrition.