The interim data obtained up to the end of the 2nd year of the nation-wide multicentric cooperative study on the long-term effects of bromocriptine in parkinsonian patients revealed the following results. Firstly, the bromocriptine monotherapy could be continued in about 40% of the patients at the mean maintenance dose of 10.8 mg daily. Secondly, the additional use of bromocriptine in parkinsonian patients already treated with levodopa had a favorable influence on late side effects of levodopa such as on-off phenomenon and dyskinesia. No significant difference has been found so far as to the management of the wearing-off phenomenon between the patients with levodopa alone and those with levodopa and bromocriptine.