Fifty patients presenting with a suspected herniated lumbar intervertebral disc were evaluated with sector computed tomography (CT). Excluded from this series were patients with prior lumbar laminectomy or a clinical diagnosis of lumbar canal stenosis. Forty-six of the patients also underwent preoperative lumbar myelography. All patients subsequently underwent laminectomy. In 40 patients (80%), CT was positive. In the remaining 10 patients (20%), it was negative; in this group the myelogram correctly predicted the lesion in 8 (80%). Sector CT correctly predicted the nature of the lesion in 24 patients (48%), was incorrect in 14 (28%), and gave incomplete findings in 12 (24%). CT was most accurate when it demonstrated a disc protrusion as the only finding. In this group, sector CT correctly predicted the operative findings in 24 of 25 patients (96%). CT was less accurate when spondylitic compression was diagnosed. This study suggests that sector CT is a useful test in the evaluation of patients with sciatica and that, when a soft herniated disc is demonstrated on CT, myelography may be omitted.