Nutritional status was determined in 17 ultramarathoners registered to participate in the Old Dominion 100-Miler. They had a mean age of 40 +/- 2 yr and ran 67.7 +/- 9.0 miles.wk-1. Subjects maintained 4-d dietary records on two occasions: usual and prerace. Fasting blood samples and 24-h urine collections were also obtained, and concentrations of selected vitamins and minerals were analyzed. Usual and prerace energy, carbohydrate and fat intakes of the ultramarathoners were not significantly different, but usual protein and alcohol intakes were significantly (P < 0.05) higher than prerace intakes. The amount of energy supplied by carbohydrates rose from a usual intake of 54.2 +/- 2.3% to 60.1 +/- 2.4% in the prerace period. Twelve subjects reported taking vitamin/mineral supplements and mean usual and prerace intakes of vitamin and minerals from food and supplements combined met the current recommendations. Biochemical indices of vitamin and mineral status were normal. However, our findings suggest that vitamin B12 metabolism may be altered in ultraendurance runners. Further research is required to determine whether ultraendurance athletes have special nutrition needs.