Randomized, double-blind, placebo-controlled. After baseline angiograms, patients were randomized to one of three arms: micronized 17-beta estradiol, 1 milligram per day; 17-beta estradiol plus medroxyprogesterone, 5 milligrams per day for twelve days per month; and placebo. Subjects in all three arms received lipid-lowering therapy, low fat/low cholesterol diet, and the HMG-CoA reductase inhibitor, pravastatin, in sufficient dosage to reduce low density lipoprotein (LDL) cholesterol levels below 130 mg/dl. The primary endpoint was progression/regression of coronary obstructive disease as measured by angiography, including the expert human panel and quantitative computer analysis. The secondary endpoint was carotid media-intima thickness determined by ultrasound. Clinical measures included lipids, lipoproteins, apolipoproteins, estradiol and medroxyprogesterone levels, urinary prostanoid metabolites, and insulin/glucose metabolism. Subjects were recruited at three centers with active coronary angiography units. Several core facilities supported the study: a Core Lipid Lab, a Reproductive Endocrine Lab, the Biostatistics Lab (Data Coordinating Center) and the Angiographic Imaging Laboratory.