['To assess associations between race/ethnicity and medication adherence, and the potential modifying effects of weight category (normal, overweight, obese) in a community-based sample.', 'We studied 1355 participants from the CARDIA (Coronary Artery Risk Development in Young Adults) study who were taking prescription medications in 2000-1. Medication adherence, as rated on the four-item Morisky medication adherence scale (score of 4 = maximum adherence), was reported for all participants.', 'The mean age ± SD of participants was 40 ± 3.6 years; 45% were African American and 36% were male. Overall, Whites had a higher proportion of maximum adherence than African Americans (59 vs 41%, respectively; p\xa0=\xa00.001). However, this difference was statistically significant only for participants within the normal weight category, of whom 54% of Whites were maximally adherent versus 35% of African Americans (p\xa0<\xa00.05). After adjustment for possible confounding covariates, race/ethnicity was associated with adherence only in those of normal weight: the odds ratio for maximum adherence in Whites versus African Americans of normal weight was 1.98 (95% CI 1.13, 3.47). Within race/ethnicity subgroups, weight category was associated with adherence in Whites but not in African Americans.'] Does obesity modify the Association of Race/Ethnicity with Medication Adherence in the CARDIA Study?