Ascorbic acid, cysteine, glutathione and uric acid were determined by reverse-phase high-pressure liquid chromatography (HPLC) in 46 breast tissue samples [neoplastic (C) and non-neoplastic (N) from the same patient]. Cholesterol, alpha-tocopherol and gamma-tocopherol were quantified in 64 similar samples by extraction into heptane followed by direct-phase HPLC. DNA was measured in all samples and the percentages of epithelium, fat and connective tissue were estimated in sections adjacent to the sample. Results confirm previous findings that ascorbic acid and glutathione, expressed as mumol/g DNA, were greatly increased in the epithelium of neoplastic tissue. Similar increases in cysteine could be accounted for by the presence of inflammatory cells. Although values of alpha- and gamma-tocopherol correlated with the percentage of fat in both types of tissue, these compounds were also present in the epithelium. Because of the varying amounts of fat in the samples, no significant difference could be found between N and C values. Cholesterol correlated with fat in N and epithelium in C. Consideration of 10 cases with equal amounts of fat in C and N tissue suggests that cholesterol is reduced in C in the epithelial cells.