It is important to identify the role of nutrition in the treatment and prevention of osteoporosis. The goal of this study was to compare the equivalency of nutrient intakes assessed by diet records and the Arizona Food Frequency Questionnaire and the associations of these nutrients with bone mineral density (BMD). This is a secondary analysis of cross-sectional data that was analyzed from six cohorts (fall 1995 to fall 1997) of postmenopausal women (n=244; 55.7+/-4.6 years) participating in a 12-month, block-randomized, clinical trial. One-year dietary intakes were assessed using 8 days of diet records and the Arizona Food Frequency Questionnaire. Participants' BMD was measured at the lumbar spine (L2-L4), femur trochanter, femur neck, Ward's triangle, and total body using dual-energy x-ray absorptiometry. Linear regression analyses (P< or =0.05) were adjusted for the effects of exercise, hormone therapy use, body weight at 1 year, years post menopause, and total energy intake. Significant correlations (r=0.30 to 0.70, P< or =0.05) between dietary assessment methods were found with all dietary intake variables. Iron and magnesium were consistently and significantly positively associated with BMD at all bone sites regardless of the dietary assessment method. Zinc, dietary calcium, phosphorous, potassium, total calcium, and fiber intakes were positively associated with BMD at three or more of the same bone sites regardless of the dietary assessment method. Protein, alcohol, caffeine, sodium, and vitamin E did not have any similar BMD associations. Diet records and the Arizona Food Frequency Questionnaire are acceptable dietary tools used to determine the associations of particular nutrients and BMD sites in healthy postmenopausal women.