OBJECTIVE: Acute coronary syndrome (ACS) encompasses unstable angina (UA), non-ST elevation myocardial infarction (NSTEMI) and ST segment myocardial infarction (STEMI). In 2007-2008 in Australia, there were 95 000 hospitalisations for ACS. There is limited data about the level of agreement between the ED and hospital discharge diagnosis. The objective of the present study is to describe the proportion of ED patients with a concordant ACS hospital discharge diagnosis and determine factors associated with this. METHODS: The present study was a retrospective case series of consecutive presentations of patients with ACS to the EDs of Southern Health, Victoria, Australia, during a 6 month period between August 2011 and January 2012. RESULTS: One thousand and twenty-eight patients diagnosed with ACS in the ED were identified. Hospital discharge diagnosis was recorded for 704 cases. The mean age was 63 years (SD 14.5) and 69 were male. One hundred and nineteen patients (16.9 ) were diagnosed with a STEMI, 322 (45.7 ) with a NSTEMI and 263 (37.4 ) with UA. There were 68.3 who had a concordant discharge diagnosis of ACS. An ED diagnosis of STEMI (87.4), English as the primary language (OR 1.81 [1.13-2.89]) and chest pain as the presenting complaint (OR 2.70 [1.72-4.23]) were associated with a concordant diagnosis of ACS. CONCLUSION: Almost one-third of patients who are admitted to the hospital with ACS have a different hospital discharge diagnosis. English as a primary language and presenting with chest pain are associated with a more concordant diagnosis. More research needs to be performed to better understand these findings.