Bromocriptine, a dopamine receptor agonist, was administered to 20 patients with idiopathic parkinsonism taking levodopa (L-dopa) or "Sinemet" (levodopa combined with carbidopa in a 10/1 ratio) at optimum doses. In a double-blind randomised cross-over study lasting 6 months, the addition of bromocriptine (mean daily dose 79 mg) led to a significant (P less than 0.01) 74% reduction in the dose of sinemet and levodopa. "Total disability score" showed a significant (P less than 0.01) improvement at both low and high doses of bromocriptine. Tremor improved 50% (P less than 0.01), with significant improvements in gait, posture, writing, balance, rigidity, finger dexterity, and drooling. Adverse reactions were similar to those observed with sinemet and levodopa. Although both the cause and the cure of idiopathic parkinsonism remain elusive, bromocriptine appears to represent a therapeutic advance.