Intravenous enoxaparin did not reduce significantly the primary end point (p = 0.06) compared with unfractionated heparin (UFH) in the randomized Acute Myocardial Infarction Treated with primary angioplasty and intravenous enoxaparin Or unfractionated heparin to Lower ischemic and bleeding events at short- and Long-term follow-up (ATOLL) trial. We present the results of the prespecified per-protocol analysis excluding patients who did not receive the treatment allocated by randomization or received both enoxaparin and UFH. We evaluated all-cause mortality, complication of myocardial infarction, procedural failure, or major bleeding (primary end point) and all-cause mortality, recurrent acute coronary syndrome, or urgent revascularization (main secondary end point). Baseline and procedural characteristics were well balanced between the 2 treatment groups. Of 910 randomized patients, 795 patients (87.4%) were treated according to the protocol with consistent anticoagulation using intravenous enoxaparin (n = 400) or UFH (n = 395). Enoxaparin reduced significantly the rates of the primary end point (relative risk [RR] 0.76, 95% confidence interval [CI] 0.62 to 0.94, p = 0.012) and the main secondary end point (RR 0.37, 95% CI 0.22 to 0.63, p <0.0001). There was less major bleeding with enoxaparin (RR 0.46, 95% CI 0.21 to 1.01, p = 0.050) contributing to the significant improvement of the net clinical benefit (RR 0.46, 95% CI 0.3 to 0.74, p = 0.0002). All-cause mortality was also reduced with enoxaparin (RR 0.36, 95% CI 0.18 to 0.74, p = 0.003). In conclusion, in the per-protocol analysis of the ATOLL trial, pertinent to >87% of the study population, enoxaparin was superior to UFH in reducing ischemic end points and mortality.