Seventy-seven patients with back pain and suspected disc prolapse were examined by computer tomography, and 41 have in addition myelograms. In 26 patients surgery was performed. The accuracy of computer tomography in the diagnosis of disc prolapse was greater than 86%, with additional myelography it was greater than 95%. Difficulties in diagnosis using computer tomography were encountered with recurrent disc prolapses. CT of the disc should be performed with a high resolution scanner using a slice thickness of 2 mm before myelography is considered. Definitely abnormal CT findings make myelography unnecessary.