The study was a randomized, double-blind, controlled trial. Subjects were randomized to conjugated estrogen with daily medroxyprogesterone or placebo within two weeks of bypass surgery. Graft occlusion and development of vein graft atherosclerosis were measured by comparing quantitative coronary angiographic and vascular ultrasonic assessment of disease severity and extent performed at six months and three and a half years after randomization. The primary outcome variables included the occurrence of graft occlusion at six months and the change in severity and extent of atherosclerosis in the saphenous vein grafts over three years. The trial determined the influence of hormone replacement therapy on the primary outcome variables.