The reproducibility of nutrient intakes measured by a semi-quantitative food frequency questionnaire were examined in 418 African American and white men and women between the ages of 45 and 64 years. Subjects were a subset of participants in the Atherosclerosis Risk in Communities (ARIC) study. Reliability coefficients were calculated for nutrient intakes reported over a mean elapsed period of three years. Reliability coefficients tended to be higher in men than in women and higher in white Americans than in African Americans. The median reliability coefficients were 0.63 in white men, 0.48 in white women, 0.50 black men, and 0.45 in black women. Reliability coefficients tended to be higher in subjects with more than 12 years of education compared to those with less education. Also, age was associated with the size of the reliability coefficients, and participants who were 45- 49 years of age tended have higher coefficients than older participants.