Subjects were randomized into a 2 x 2 factorial trial of hormone replacement therapy and antioxidant therapy. Women were randomized into four treatment groups: both active hormone replacement and antioxidant; active hormone replacement therapy and antioxidant placebo; active antioxidant therapy and hormone replacement placebo; double placebo plus usual care. Hormone replacement therapy consisted of estrogen plus a progestin (PremPro) for all gynecologically intact women, and unopposed estrogen (Premarin) for women with hysterectomies. Antioxidants consisted of a combination of vitamin E and vitamin C. Angiographic change was a primary endpoint of this trial. The study was double-blind to the extent permitted by the interventions; however, it was fully-blinded with respect to outcome variables. Recruitment ended in August 1999. The mean duration of follow-up was approximately three years.