The National Cholesterol Education Program Adult Treatment Panel III recommends an algorithm to integrate iterative risk-stratification information with low-density lipoprotein (LDL) cholesterol levels to identify candidates for statin therapy. We used the Aggrastat to Zocor (A to Z) trial, in which all patients presented with an acute coronary syndrome (ACS) event in the absence of previous statin therapy, to evaluate the performance of this algorithm. Of 1,750 patients with ACS included in this analysis, 1,126 (64%) had an indication for statin therapy before enrollment and 624 (36%) did not have a statin indication before enrollment. We estimate that initiating statin therapy at moderate dosages (decreasing LDL by 1 mmol/L) according to the National Cholesterol Education Program Adult Treatment Panel III guidelines would have prevented approximately 15% of the ACS events leading to enrollment in the A to Z trial, whereas more intensive statin therapy (decreasing LDL by 1.5 mmol/L) would have prevented >21% of events. Aspirin use before enrollment was reported in only 38% of subjects with a statin indication. In conclusion, these observations represent missed opportunities for primary and secondary prevention and highlight the need for assessment of patient risk and better adherence to existing prevention guidelines.