['There is conflicting information about whether nitrate treatment aggravates long-term prognosis, so the present retrospective study was designed to determine the effects of long-term nitrate therapy on major adverse events after acute myocardial infarction (AMI) in the coronary interventional era.', 'Using the Japanese Acute Coronary Syndrome Study database, 1,236 consecutive patients who were hospitalized within 48 h of onset of symptoms of AMI from January to December 2003 were evaluated. All-cause mortality, cardiac events and cardiovascular events were lower in patients treated with nitrates than in the untreated controls. However, these crude comparisons included several confounding factors on nitrate prescription. To minimize the effect of selection bias on outcomes, the technique of propensity score matching for clinical characteristics was used and distortion of effective nitrate treatment was excluded as much as possible. The results of propensity score matching showed that nitrate therapy had no impact on all-cause mortality, cardiac events and cardiovascular events at 30, 60 or 90 days, 6 months, 1 year, and 2 years follow-up.'] Does long-term nitrate therapy after acute myocardial infarction improve or aggravate prognosis?