Aims: To compare ST-segment elevation myocardial infarction (STEMI) and non-STEMI (NSTEMI) mortality between Sweden and the UK, adjusting for background population rates of expected death, case mix, and treatments. Methods and results: National data were collected from hospitals in Sweden [n = 73 hospitals, 180 368 patients, Swedish Web-system for Enhancement and Development of Evidence-based care in Heart disease Evaluated According to Recommended Therapies (SWEDEHEART)] and the UK [n = 247, 662 529 patients, Myocardial Ischaemia National Audit Project (MINAP)] between 2003 and 2013. There were lower rates of revascularization [STEMI (43.8% vs. 74.9%); NSTEMI (27.5% vs. 43.6%)] and pharmacotherapies at time of hospital discharge including [aspirin (82.9% vs. 90.2%) and (79.9% vs. 88.0%), β-blockers (73.4% vs. 86.4%) and (65.3% vs. 85.1%)] in the UK compared with Sweden, respectively. Standardized net probability of death (NPD) between admission and 1 month was higher in the UK for STEMI [8.0 (95% confidence interval 7.4-8.5) vs. 6.7 (6.5-6.9)] and NSTEMI [6.8 (6.4-7.2) vs. 4.9 (4.7-5.0)]. Between 6 months and 1 year and more than 1 year, NPD remained higher in the UK for NSTEMI [2.9 (2.5-3.3) vs. 2.3 (2.2-2.5)] and [21.4 (20.0-22.8) vs. 18.3 (17.6-19.0)], but was similar for STEMI [0.7 (0.4-1.0) vs. 0.9 (0.7-1.0)] and [8.4 (6.7-10.1) vs. 8.3 (7.5-9.1)]. Conclusion: Short-term mortality following STEMI and NSTEMI was higher in the UK compared with Sweden. Mid-and longer-term mortality remained higher in the UK for NSTEMI but was similar for STEMI. Differences in mortality may be due to differential use of guideline-indicated treatments.