Twenty-six patients with clinically confirmed mammary dysplasia and five age-matched controls were treated with alpha-tocopherol, 600 mg/day. Serum samples collected on the 21st day of the menstrual cycle were analyzed for cholesterol in lipoprotein fractions, isolated by a combination of precipitation and ultracentrifugation techniques. Eighty-five percent of patients showed objective and subjective remission from disease following therapy. In mammary dysplasia patients, the ratio of serum cholesterol/high density lipoprotein cholesterol was higher than those in age-matched controls, an abnormality which was corrected by alpha-tocopherol therapy. Furthermore, as a result of therapy, high density lipoproteins increased and ester cholesterol associated with low density lipoproteins decreased. The results suggest that alpha-tocopherol may serve as an effective agent in treating patients with benign disease, as well as correct the inherent abnormality in serum cholesterol distribution in mammary dysplasia patients.