Purpose: The aim of this study was to investigate the frequency and gender distribution of variations in the aortic arch branching pattern using 64-slice computed tomograhic angiography. Materials and methods: A total of 1000 patients with a normal left-sided aortic arch who underwent computed tomographic angiography for various reasons were analysed retrospectively for the frequency of variation of aortic arch branching; the variations were categorised into seven types. Results: Of the 1000 patients, 79.2% had a normal aortic arch branching pattern - type 1 - and 20.8% had variations. The frequency of type 2 variation - brachiocephalic and left common carotid arteries arising from the aortic arch in a common trunk - was 14.1%, that of type 3 - left vertebral artery originating from the aortic arch - was 4.1%, that of type 4 - coexistence of type 2 and type 3 - was 1.2%, that of type 5 - aberrant right subclavian artery - was 0.6%, that of type 6 - coexistence of aberrant right subclavian artery and bicarotid trunk - was 0.7%, and that for type 7 - thyroidea ima artery arising from the aortic arch - was 0.1%. The incidences of the variations of aortic arch branching were similar among males and females (20% versus 22.1%). The incidence of an aberrant right subclavian artery - type 5 and type 6 - was higher among females compared with males (2.5% versus 0.5), whereas the frequencies of the other variations were either equal or similar in both genders. Conclusion: Recognition of variations of aortic arch branching is important because they may cause symptoms due to tracheoesophageal compression or complications during surgical or endovascular interventional procedures of the aorta and its branches.