Summary. Introduction and development. Selective inhibitors of peripheral catechol-O-methyltransferase (COMT) seem to be useful drugs for the treatment of patients with Parkinson’s disease. When associated with levadopa and a dopa-decarboxylase inhibitor they are clearly effective in patients with progressive illness, who are particularly dependent on the plasma concentration of levadopa, or may have fluctuating motor function when the effect of the dose is wearing off. Entacapone, a prototype of this group of drugs, has been shown to modify the pharmacokinetics of levadopa in such a way that the plasma concentration of levadopa is raised (between 21% and 50% in different studies); to reduce variations in plasma level between doses, which allows some patients to reduce the total daily dose of levadopa at the same time as the response time (time ‘on’) increases by between 20% and 78%. Conclusion. Entacapone is a well tolerated drug and could form part of a regular ‘triple therapy’ in the patients described