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Long term recalls of dietary intake are frequently used in case-control studies, but their validity and reliability have not been established. In this study, 91 middle-aged adults (median age, 50 years) who were participants in the Longitudinal Study of Child Health and Development at the Harvard School of Public Health in Boston, Massachusetts, starting in the early 1930s, were asked in 1984-1985 to report present food intake and to recall food intakes at ages 5-7 years. 18 years, and 30 years using food frequency questionnaires. Their recalled intakes were validated by comparison with historical records of intake collected during the earlier time periods. Recall of food intake in the distant past was a better predictor of historical intake than was current diet. However, correlations between recalled and historical consumption for individual foods and food groups were generally low, rarely exceeding 0.3. Current intakes exerted a powerful influence on accuracy of recall. The consideration of participant characteristics did not prove to be consistently useful in explaining variations in food item and food group-related recall. The authors conclude that recall of food intake in the distant past may be a sufficiently valid estimate of past intake to justify its collection.