Intravenously administered levodopa is effective although relatively impractical for the chronic treatment of patients with Parkinson's disease who are disabled by motor fluctuation. In view of its greater solubility, levodopa methyl ester (LDME) was evaluated in seven advanced parkinsonian patients as a potentially more convenient alternative. Compared with oral levodopa, LDME infusions resulted in marked reductions of both plasma levodopa variations and motor response fluctuations in patients with either wearing-off or on-off phenomena. During infusions lasting approximately 1 week, there were no complications except for peripheral vein phlebitis. The results suggest that LDME might be a practical parenteral treatment for those with severe Parkinson's disease. It appears that central venous access or its equivalent will be necessary for its chronic administration.