Two cases of fourth-degree spondylolisthesis of the fifth lumbar vertebra with cauda equina compression are reported. In the first patient, arthrodesis in the position of deformity failed to relieve neural compression and subsequent decompression by osteoplasty of the sacrum was necessary. In the second patient, partial reduction of the vertebral displacement was achieved by skeletal traction before and after decompression and lateral fusion. It is suggested that reduction and maintenance of reduction in selected cases of severe spondylolisthesis is both desirable and obtainable.