Participating in the study were 22 clinical centers across the United States, a coordinating center, central laboratory, two ECG reading centers, and lipid standardization laboratory, as well as a drug distribution center. The trial has concluded, with the main mortality results published in September l982. Active follow-up was terminated on schedule on February 28, l982, with final determination of vital status as of that date accomplished for 99.6 percent of the study population.