The Air Force/Texas Coronary Atherosclerosis Prevention Study (AFCAPS/TexCAPS) first reported its results in 1998, before the 2001 publication of the National Cholesterol Education Program-Adult Treatment Panel III guidelines (NCEP-ATP III) and 2004 update. Our objective was to investigate the impact of these guidelines on the AFCAPS/TexCAPS cohort. The main outcome measures were the event rates of first acute major coronary events (AMCEs), which were reduced 39% by lovastatin (95% confidence interval [CI] 21% to 53%, p <0.001) in the 65% of the cohort eligible for drug therapy and by 34% (95% CI -9% to 60%, p = 0.108) in the remaining 35% for whom drug therapy was considered optional. The evaluation of other guideline components included a 44% (95% CI 27% to 58%, p <0.001) reduction in AMCEs in subjects with baseline high-density lipoprotein cholesterol <40 mg/dl and a 41% (95% CI 19% to 57%) reduction in AMCEs in subjects with the metabolic syndrome. In the recent update, patients who had a moderately high risk of coronary heart disease and a baseline low-density lipoprotein cholesterol level of 100 to 130 mg/dl could be considered for therapy with a medication to lower the low-density lipoprotein cholesterol level to <100 mg/dl. A total of 334 subjects (5.1%) were in this group, in whom lovastatin reduced the risk of AMCEs by 68% (95% CI 12% to 88%, p = 0.027). However, 21% of the AMCEs were missed by the guidelines. Metabolic syndrome was noted in 48% of these subjects and may help define those in whom treatment with a medication is now considered optional. In conclusion, the ability of the ATP III guidelines and its update has markedly improved our ability to define coronary heart disease risk; however, other components of the guidelines, such as non-high-density lipoprotein cholesterol and the optional low-density lipoprotein cholesterol target goal of <100 mg/dl, still require additional evaluation.