OBJECTIVE We sought to analyze the disease-free intervals and calculate the freedom from atherosclerosis events in the Program on the Surgical Control of the Hyperlipidemias (POSCH). BACKGROUND The POSCH study was a randomized, secondary lipid/atherosclerosis intervention trial that provided strong evidence for reduction in atherosclerosis progression as demonstrated by clinical and arteriographic end points. The 417 control group patients received American Heart Association phase II diet instruction, and the 421 intervention group patients received identical dietary instruction and underwent a partial ileal bypass operation. METHODS Four outcome measures were determined: 1) overall mortality, 2) coronary heart disease mortality, 3) coronary heart disease mortality and confirmed nonfatal myocardial infarction, and 4) coronary/cardiac interventions. RESULTS An overall mortality rate of 10% occurred at 6.7 years in the control group and 9.4 years in the intervention group, for a gain in disease-free interval of 2.7 years in the intervention group (p = 0.032). A coronary heart disease mortality rate of 8% occurred at 7.2 years in the control group and 11 years in the intervention group, for a gain of 3.8 years (p = 0.046). Twenty percent of patients demonstrated the combined end point of coronary heart disease mortality and confirmed nonfatal myocardial infarction at 5.9 years in the control group and 11.4 years in the intervention group, for a gain of 5.5 years (p < 0.001). Twenty-five percent of patients underwent either coronary artery bypass graft surgery, percutaneous transluminal coronary angioplasty or heart transplantation at 5.4 years in the control group and 12.4 years in the intervention group, for a gain of 7 years (p < 0.001). CONCLUSIONS The marked lipid modification achieved by partial ileal bypass in the POSCH trial led to demonstrable increases in the disease-free intervals for overall mortality, coronary heart disease mortality, coronary heart disease mortality and confirmed nonfatal myocardial infarction, and coronary intervention procedures. For the clinician and the patient, estimation of disease-free intervals may be more relevant than assessment of differences in incidence rates and risk ratios.