CHYMOPAPAIN, by direct injection into the intervertebral disc, will cause dissolution of the nucleus pulposus in rabbits without apparent effect on the surrounding tissues, such as ligaments, bone, nerve roots, and dura mater. 1 This technique was therefore applied to 22 dogs with paralysis of the hind legs believed to be due to herniation of intervertebral discs. Chymopapain, 1 to 5 mg, was injected directly into the discs apparently involved. Fourteen of the 22 dogs recovered to the extent of being able to stand orwalk. Seven dogs were unimproved. At autopsy, six of these dogs showed herniation or extrusion of the disc at levels other than those injected. The seventh had complete degeneration of the spinal cord below the level of the lesion. No deleterious effects of the enzyme were found in any of these animals. 2 With these favorable experiences as a foundation, clinical trials were started in July, 1963, on humans with sciatica secondary to herniated intervertebral discs. This report deals with the clinical