Eleven patients suffering from idiopathic Parkinson’s disease participated in an open study of Madopar HBS. At the beginning the patients were switched form standard Madopar to Madopar HBS, initially keeping constant L-dopa dosage and the number of daily doses. In 9 of the 11 patients a marked deterioration occurred within a few days. In spite of increasing the daily dosage of L-dopa the conditon remained unsatisfactory in several patients and forced us to prematurely discontinue the study in 5 cases. The Webster ratings improved in 1 patient, remained unchanged in 4 cases and a definite worsening occurred in 6 patients. Fluctuations of the symptomatology were improved in none of our patients. It is not excluded that these negative results might have been improved by a further increase of Madopar HBS, a less abrupt switch from standard Madopar to Madopar HBS and probably also a combination of the two forms.