Clinical response to a new galenic formulation of levodopa plus benserazide, Madopar HBS, was studied in 25 fluctuating parkinsonians. This open study was planned in two phases. In the first phase, the administering of HBS alone resulted in a surprisingly high number of dropouts. In the second phase, Madopar standard in association with Madopar HBS, the follow-up period was 24 months. A stable long-lasting improvement in predictable fluctuations and their severity was maintained for the whole period without any change in drug dose. Nocturnal and early morning akinesia improved too. The study shows that Madopar HBS plus Madopar standard is effective in producing a prolonged and stable response in parkinsonian fluctuating patients.