The Coronary Drug Project (CDP) was undertaken to evaluate the efficacy of several lipid lowering drugs on the mortality and morbidity from Coronary Heart Disease in men aged 30 to 64 who had survived at least one documented myocardial infarct and were categorized as NYHA functional Class I or II. One hundred sixty eligible males who form part of a cohort of 8,341 patients in 53 clinical centers throughout the United States were enrolled in our clinic between 1967 and 1969, and have now been followed between 44 and 66 months. Each patient was randomly assigned at entry to one of the following six treatment groups: Mixed conjugated equine estrogens (two dosage levels), clofibrate, dextrothyroxine, nicotinic acid and placebo. Eligible patients in the high dose estrogen and dextro-thyroxine groups have recently been randomly assigned in a double blind manner to Aspirin or Placebo. All patients will be followed until death or until February 28, 1975, which is the date patient participation will terminate. As an ancillary study, Clinic #34 will study the prognostic significance of cardiac arrhythmias as determined from serial 12 hour Holter ECG tape recordings in surviving patients attending Clinics #34, 07 (U.S. Public Health Service Hospital of Baltimore), and 43 (Greater Baltimore Medical Center). The quality and quantity of ventricular ectopic activity will be evaluated as an independent risk factor in comparison with multiple variables accrued from CDP central files and analyzed by modern techniques of multivariate statistical analysis. This ancillary project will form part of a larger ancillary project involving CDP Clinics in Chicago and Minneapolis, titled "Cardiac Function and Prognosis of Coronary Disease".