A total of 66 consecutive patients with severe spasticity of spinal cord origin were screened with intrathecal baclofen, and all but two responded with a two-point decrease in their Ashworth spasticity scale and/or spasm scale score. Of these, 62 elected to receive chronic intrathecal baclofen administration by means of an implanted delivery system. These patients have been followed for an average of 30 months (the first three for 81 months). Intrathecal baclofen has been well tolerated and all serious side effects were transient and have been managed by dose adjustments. The pump presently available has worked safely; the only problem has been stalling in 7% of these devices. The catheter system has had to be repaired in just over one-half of the patients and is the main cause of interruption of drug delivery. Of the 62 patients implanted, 52 (84%) continue to be treated adequately for spasticity; there are three poor long-term responders, four deaths due to underlying disease, and three whose participation has been voluntarily withdrawn. It is suggested that long-term control of spinal spasticity by intrathecal baclofen can be achieved in most patients.