OBJECTIVES: To characterise patients with atrial fibrillation (AF) in a UK secondary care centre. METHODS: Eligible patients admitted to Llandough Hospital (Cardiff, UK) as an emergency with AF (ICD10 code: I48X), and discharged between 1/10/2009 and 31/03/2010, were identified through examination of electronic patient records. Exclusion criteria included patients with atrial flutter (AFl), or an ICD10 code indicating prior inpatient attendance for AF since 1995. Patient notes were reviewed manually and an anonymised data collection template completed by the clinician for analysis. RESULTS: Of the 126 patients meeting the inclusion criteria, the notes of 7 patients were unobtainable and 8 with a diagnosis of AFl were excluded. The majority of patients were symptomatic at presentation (56%) and less than half were male (41%). Within the study population, the frequency of patients with AF increased with age, peaking at 80-89 years (45% of the study sample). Method of admission was primarily through A&E or GP referral (48% each); with 50% of A&E admissions being for symptomatic AF, compared with 60% of those referred via a GP. Almost half the study population were recorded with “first detected AF” (47%); 67% of whom were symptomatic, compared to 47% being symptomatic in patients recorded as “not first detected AF”. The majority of patients were reported to have 1 or 2 of the pre-defined co-morbidities of interest (29% each); one fifth had no co-morbidities. The most common co-morbidities were hypertension (51%), ischaemic heart disease (20%), heart failure (18%), diabetes (16%) and pulmonary disease (15%). CONCLUSIONS: Results from this study demonstrate the majority of patients presenting to secondary care with AF have multiple associated co-morbidities, which are known to influence the management and treatment strategy, and long-term complications.  Further up-to-date epidemiological studies, which describe the history, management and prognosis of patients with AF, are required.