Dietary supplements have been suggested to have a role in cancer prevention and treatment. The purpose of this study was to describe the nutrient intakes from foods and dietary supplements in women at the time of enrollment into a clinical trial to prevent breast cancer recurrence. Subjects were within four years of diagnosis with Stage I, II, or IIIA breast cancer and had completed medical treatment (n = 435). Intakes were assessed with four 24-hour recalls over two weeks. Dietary nutrient intakes in supplement users were compared with intakes in nonusers, and supplement nutrient intakes in participants consuming diets providing < 75% were compared with those in participants consuming > or = 75% of recommended levels. Intakes of participants with diets meeting general guidelines for disease prevention were compared with intakes of those whose diets did not meet these guidelines. Dietary supplement use was reported by 352 (80.9%) of the participants, but frequency of excess intakes did not exceed 5% for all micronutrients examined. Women whose diets provided higher levels of most vitamins and minerals were more likely to obtain additional amounts of these micronutrients from dietary supplements. Participants reporting use of any supplement consumed diets providing more dietary fiber (p < 0.04) and less dietary fat (p < 0.001) than nonusers of any supplement. These results illustrate the importance of monitoring dietary supplement use in clinical trials with a focus on preventing cancer recurrence, because supplements can contribute substantially to nutrient intakes in the population under study.