Objective: To ascertain the use of secondary prevention medications and cardiac rehabilitation after an acute coronary syndrome (ACS) and the impact on 2-year outcomes. Methods: CONCORDANCE (Cooperative National Registry of Acute Coronary care, Guideline Adherence and Clinical Events) is a prospective, observational registry of 41 Australian hospitals. A representative sample of 6859 patients with an ACS and 6 months' follow-up on 31 May 2016 were included. The main outcome measure was use of ≥75% of indicated medications (≥4/5 (or ≥3/4 if contraindicated) of angiotensin-converting enzyme (ACE) inhibitor/angiotensin receptor blocker, beta-blocker, lipid-lowering therapy, aspirin and other antiplatelet). Major adverse cardiovascular events (MACE) included myocardial infarction, stroke or cardiovascular death. Results: The mean age was 65±13 years, 29% were women, and the mean Global Registry of Acute Coronary Events (GRACE) score was 106±30. At discharge, 92% were on aspirin, 93% lipid-lowering therapy, 78% beta-blocker, 74% ACE/angiotensin receptor blocker and 73% a second antiplatelet; 89% were taking ≥75% of medications at discharge, 78% at 6 months and 66% at 2 years. At 6 months, 38% attended cardiac rehabilitation, 58% received dietary advice and 32% of smokers reported quitting. Among 1896 patients followed to 2 years, death/MACE was less frequent among patients on ≥75% vs <75% of medications (8.3% vs 13.9%; adjusted OR 0.75, 95 % CI 0.56 to 0.99), and was less frequent in patients who attended versus who did not attend cardiac rehabilitation (4.6% vs 13.4%; adjusted OR 0.44, 95% CI 0.31 to 0.62). Conclusions: Use of secondary prevention therapies diminishes over time following an ACS. Patients receiving secondary prevention had decreased rates of death and MACE at 2 years.