Epidural venography was performed in 110 patients with suspected lumbar-disc herniation by catheterization of the ascending lumbar and ascending sacral veins. The findings by venography and by myelography were compared with those revealed by operative exploration. Only sixty-one patients had venography, myelography, and operative exploration. In fifty of these patients with no previous disc surgery, the diagnostic accuracy of venography was 98 per cent and of myelography, 90 per cent. Venography had limited value in the other eleven patients who had had one or more prior disc operations because it did not distinguish between scarring and recurrent disc herniation at the levels previously explored. Selctive ascending lumbosacral venography is indicated both in patients who have not had a prior disc operation, as a guide to whether myelography should be performed when the clinical picture is ambiguous, and in patients whose myelogram is normal or equivocal but whose signs and symptoms are strongly suggestive of disc herniation.