Seventeen hitherto untreated patients with mild Parkinson's disease were given the dopamine agonists mesulergine or pergolide. Of the 10 patients who received pergolide (mean dosage 3.7 mg/day) five failed to improve, four showed slight improvement and one gained moderate benefit. Of the seven patients who received mesulergine (mean dose 6.4 mg/day) three patients derived no benefit, two slight benefit and two moderate benefit. The incidence of adverse side-effects was high with both drugs despite the use of a peripheral dopamine receptor antagonist, domperidone, when required. These results are less encouraging than those reported from other centres both in respect of response rate and the severity of unwanted effects.