The assessment of acetabular fractures by conventional radiology is difficult whilst essential to the planning of orthopaedic treatment. This report details the results of computed tomography (CT) in a study of acetabular fractures in 30 patients. Computed tomography was always superior to conventional radiology, particularly in the evaluation of lesions of the posterior acetabular margin. The standard classification of the fractures did not require modification but was reinforced by the three-dimensional visualisation of the lesions. The particular contribution of CT was in the assessment of associated lesions often not apparent on conventional views of the pelvis: these comprised sacroiliac lesions in 60% of cases, intra-articular loose bodies in 33% of cases and pelvic haematomas in 17% of cases. As a result of CT, treatment was changed in one third of cases. In addition to its role in indicating the need for surgical or orthopaedic treatment, CT sometimes permitted a better choice of surgical technique, especially in respect of sacroiliac lesions causing as yet unexplained sciatica.