Forty-six patients with Parkinson's disease experiencing motor fluctuations and not optimally controlled on levodopa received as adjunct therapy a new nonergoline dopamine agonist, ropinirole, in a 3-month randomized placebo-controlled trial. Ropinirole significantly reduced the duration of off periods as assessed by self-scoring diary cards. There were more nonserious dopaminergic adverse events in the ropinirole group. More patients withdrew because of adverse events or insufficient therapeutic effect in the placebo group. Ropinirole has beneficial adjuvant effects in parkinsonian patients with moderate motor disability and motor fluctuations.