Injuries to the lateral ligaments of the ankle are common in medical practice. The most commonly injured ligaments are the anterior talofibular (ATFL) and calcaneofibular (CFL) ligaments. When undertaking MRI evaluation of ankle injuries it is important to understand the normal dimensions, appearance and variations of these ligaments. Twenty-eight consecutive patients referred for MRI of the ankle underwent bilateral scanning. The thickness of normal and abnormal ATFL and CFL was determined. The mean thickness of the ATFL was 2.19 +/- 0.6 mm and the CFL measured 2.13 +/- 0.5 mm. One normal ankle had an extremely thin ATFL (0.8 mm) with an otherwise normal appearance, whereas two ankles had an ATFL with a high attachment, both of which were deemed to be normal variants. Nineteen per cent of normal CFLs were noted to consist of a lateral hypointense band with a medial isointense medial band. Two variations of normal ATFL, one normal variant CFL and a measurement of the normal thickness of the ATFL and CFL have been presented in this paper. These variations have not been described previously by other authors. It is envisaged that these findings will assist in the MRI assessment of the lateral ankle ligaments.