In 1972, the Multiple Risk Factor Intervention Trial began recruiting 12,866 men, ages 35 to 57, selected for elevation of one or more risk factors but free from coronary heart disease and followed them for an average of seven years after randomization to a risk factor modification group or to a control group referred to their own physicians for treatment. The serum from MRFIT had been stored since 1972. Detailed follow-up for the cohort was completed through 1985 and was extended through 1988 using the National Death Index.