BACKGROUND : Emergency department (ED) frequent attenders (FAs) have a higher rate of adverse outcomes compared to infrequent attenders. OBJECTIVE : The primary aim was to describe the prevalence of FAs at an inner city ED. A subgroup analysis was undertaken for high and very high FAs to establish demographics and other factors which might cause them to attend frequently. METHODS : A retrospective review of all patients who attended the ED at Mercy University Hospital (MUH), Cork, during 2016 was undertaken. Patients were classified as either infrequent attenders (1-2 attendances/year), frequent attenders (3-12 attendances/year), high frequent attenders (HFA, 13-29 attendances/year), or very high frequent attenders (VHFA, > 30 attendances/year). RESULTS : During 2016, a total of 21,920 patients presented 33,152 times. Overall, 90.2% (n = 19,761) were infrequent attenders, whilst 9.6% (n = 2115) were FAs. A further 36 patients (0.16%) were HFAs and eight patients (0.04%) were classified as VHFAs. Almost 10% of patients attended the ED three or more times, accounting for 29% of overall ED attendances. The HFA and VHFA cohorts were predominantly male (79.5%, n = 35) with an average age of 49.6 years. They were found to have multiple medical comorbidities, complex psychosocial problems, and a mortality rate of 11.3% over a 2-year period. CONCLUSIONS : This retrospective review is the most detailed assessment of Irish FAs undertaken to date. Further studies are required to examine the Irish hospitals most at need of Case Management Strategy Programmes which we postulate could minimise the risk of adverse outcomes for these patients and improve overall ED efficiency.