Baclofen (a gamma aminobutylic acid derivative) and a placebo were compared for their efficacy in relieving certain symptoms in patients with long-standing spinal cord lesions and "spinal spasticity." In a double-blind, cross-over clinical investigation, 22 patients with chronic spinal cord disease were studied. Baclofen regularly alleviated involuntary flexor or extensor spasms and increased resistance to passive movement of the legs but did not alter strength, gait, stretch reflexes, or clonus. Side effects were mild and transient. This study demonstrates that (1) baclofen is useful for the treatment of flexor spasms and (2) in evaluating a new mode of therapy, one must consider selectively the response of individual components of such global syndromes as "spasticity."