Subcutaneous lisuride infusion in Parkinson's disease. Response to chronic administration in 34 patients. Thirty-eight parkinsonian patients with motor fluctuations and dyskinesias on chronic levodopa therapy were treated with subcutaneous lisuride infusion (SLI). Thirty-six were discharged from hospital on combined treatment with 24 h lisuride infusion (111.3 +/- 29.5 micrograms/h) and oral levodopa plus a decarboxylase inhibitor (729.6 +/- 452 mg/day); all obtained a marked initial improvement in mobility (mean reduction 'off' hours 87.5%); 34 were followed for a mean of 20.85 (range 6-45) months. Most patients continued to show improvement with respect to baseline assessment during chronic treatment but 23 developed dyskinesias, 'off' periods or both, which were difficult to control by changing the levodopa schedule, lisuride dose or both. In only 5 patients was lisuride treatment stopped because of inefficacy. The high incidence of psychiatric side-effects (18/38) was the major limiting factor for continuing lisuride infusion in this population of severe parkinsonian patients. Many complained about the inconvenience of the pump's technical requirements for long-term utilization, but only 4 patients abandoned SLI for this reason. These results indicate that motor function may be substantially improved in severe parkinsonian patients treated with SLI but increased dyskinesia or psychiatric adverse effects limited the long-term usefulness of this approach. It is suggested that continuous dopaminergic stimulation may be a particularly useful therapeutic strategy when applied in earlier stages of the disease. 