The validity of two dietary history questionnaires was examined, one the Health Habits and History Questionnaire (HHHQ) developed by Block et al and the other a questionnaire developed by investigators at the University of Michigan (UM). The reference data consisted of the mean of four 4-day dietary records and recalls collected for 1 year before administration of the questionnaires. The sample of 85 persons included black and white men and women aged 25 to 50 years. The HHHQ was entirely self-administered; the UM questionnaire had both self- and interviewer-administered components. The HHHQ group means were similar to food record estimates for energy and most nutrients, whereas the UM questionnaire produced overestimates for energy and all nutrients examined. Correlations ranged from .31 to .60 (median = .48) for the UM questionnaire and from .42 to .68 (median = .57) for the HHHQ. Use of respondent-reported portion sizes with the HHHQ produced higher correlations than use of investigator-determined "standard" portion sizes (median r = .43 vs .57). Food frequency questionnaires can provide useful nutrient data for individuals as well as groups.