Twenty patients with Parkinson's disease were treated with the 8-alpha-ergoline derivative mesulergine. Participants were divided into two groups, and over a nine-week period, mesulergine dosage was increased to a maximum of either 10 or 20 mg daily. During this time levodopa-carbidopa (LD-CD) dosage was reduced and treatment was discontinued if possible. The dosage of LD-CD was reduced 75% in the 10 mg group and 74% in the 20 mg group. Patients in the low-dose group maintained their functional status and showed improvement in postural stability. Patients in the high-dose group showed improvement in each of the cardinal signs of parkinsonism. Adverse effects were generally mild and infrequent. Many adverse effects induced by LD-CD diminished or resolved. Our results suggest that mesulergine can be valuable in the management of Parkinson's disease, particularly in those individuals experiencing dose-limiting adverse effects from LD-CD.