Ten healthy male volunteers participated in this Phase I multiple dose study with CV-2619 (6-[10-hydroxydecyl]-2,3- dimethoxy-5-methyl-1,4-benzoquinone, idebenone). Each volunteer received single oral doses of 100 mg CV-2619 on study days 1 and 35, and during days 2 to 34, 300 mg daily in three divided doses. Blood and urine samples were collected for pharmacokinetic analysis of CV-2619 and its two major metabolites. CV-2619 was well tolerated with regard to the subjective and objective assessments made during the study. There were no changes in clinical laboratory values which could be directly attributed to the administration of CV-2619. The elimination of CV-2619 appeared to be biphasic with a mean terminal elimination half-life of 18 h. Levels of metabolites in serum were too low to provide adequate description of their elimination kinetics. CV-2619 and its metabolites showed no tendency to accumulate over the 35-day period.