Computed tomography represents one of the most remarkable short-term technical advances ever seen in medicine. Its recent extension to scanning of the lumbar spine promises to become its most significant extracranial application. The accusation has been made that CT scanning represents an expensive diagnostic modality whose cost is unjustified by its clinical value. Recent studies indicate that CT scanning is presently costeffective and promises to become more so in the future, not only by decreasing the cost of instrumentation but also by replacing other diagnostic tests (particularly those of an invasive type) and lessening the need for exploratory surgery. CT scanning is of direct benefit to the patient because it assures that lumbar surgery is performed only after an accurate and complete diagnosis.