Mortality after 10 1/2 years for hypertensive participants in the Multiple Risk Factor Intervention Trial The Multiple Risk Factor Intervention Trial (MRFIT) is a randomized primary prevention trial that tested the effect of a multifactor intervention program on coronary heart disease (CHD) mortality in 12,866 high-risk men aged 35-57 years. Men were randomly assigned to either a special intervention (SI) program, which consisted of dietary advice for lowering blood cholesterol levels, counseling aimed at cessation for cigarette smokers, and stepped-care treatment for hypertension for those with elevated blood pressure, or to their usual sources of health care within the community (UC). Among the 12,866 randomized men, 8,012 (62%) were hypertensive at baseline. For this subgroup, mortality rates with 10.5 years of follow-up were lower for the SI than for the UC group by 15% (p = 0.19) for CHD and 11% (p = 0.13) for all causes. These results reflected more favorable outcomes for SI compared with UC hypertensive men during the 3.8 posttrial years (March 1982 through December 1985) than during the preceding 6-8 years (through February 1982). During the posttrial years, death rates were lower for SI than for UC men by 26% (p = 0.09) for CHD and 23% (p = 0.02) for all causes. For those with diastolic blood pressure equal to or more than 100 mm Hg, this posttrial trend was a continuation of a trend during the trial; therefore, with 10.5 years of follow-up, death rates were markedly lower for SI than for UC by 36% (p = 0.07) for CHD and 50% (p = 0.0001) for all causes. Similarly, for those without baseline resting electrocardiographic abnormalities, the favorable posttrial outcome for the SI group was a continuation of a trend during the trial. In contrast, for those with baseline diastolic blood pressure of 90-99 mm Hg and for those with baseline resting electrocardiographic abnormalities, the favorable posttrial mortality findings for the SI group were a reversal of unfavorable trends recorded during the trial. Two factors appear to have contributed to this more favorable mortality trend for the SI group: 1) a change in the diuretic treatment protocol for SI men about 5 years after randomization, which involved replacement of hydrochlorothiazide with chlorthalidone at a daily maximum dose of 50 mg; and 2) a favorable effect of intervention on nonfatal cardiovascular events during the trial years. In addition, delay until the full impact of beneficial effects on mortality end points from smoking cessation and cholesterol lowering could have contributed.(ABSTRACT TRUNCATED AT 400 WORDS). 