A total of 89 subjects including 30 breast cancer patients with distal metastases, 29 patients with benign breast disease, and 30 healthy subjects were studied. Serum samples from these subjects were obtained from the National Cancer Institute (NCI) Breast Cancer Serum Bank, Bethesda. Serum concentrations of vitamin A and its transport proteins (prealbumin and retinol-binding protein [RBP]), beta-carotene, vitamin E, and selenium were determined. For each of these parameters the mean for the breast cancer patients was lower than that of the healthy subjects. The differences between healthy subjects and patients with either breast cancer or benign breast disease were, however, statistically significant only in the case of RBP (p less than 0.05). In the case of vitamin A and its transport proteins these differences were reduced by comparing the cancer patients with the benign breast disease patients rather than with the healthy controls. This indicates that the low serum levels for those three parameters may be merely a consequence of disease in general rather than a feature of cancer per se.