In this prospective cohort study, participants completed a mailed general medical and health questionnaire at baseline and an intensively validated semiquantitative food frequency questionnaire (SFFQ). At one year, tissue specimens were collected and catalogued for future nested case-control analyses of coronary heart disease risk in relation to levels of calcium, selenium, and chromium. Follow-up questionnaires to update exposure information and ascertain non-fatal endpoints were mailed at two-year intervals. All reported cases of non-fatal myocardial infarction, stroke, and cancer were documented with hospital records and/or pathology reports. Fatal events were ascertained with the National Death Index and documented. To standardize SFFQ nutrient scores against measurements of absolute intake, two one-week diet records were obtained from a random sample of 150 Boston-area participants.