Coenzyme Q10 (ubidecarenone; CoQ10) was administered at a dose of 60 mg/d either using two conventional formulations or in a lipid microsphere to dogs. Plasma concentrations of CoQ10 were determined by HPLC. The bioavailability of CoQ10 from the lipid microsphere formulation was superior to conventional formulations. These results suggest that three daily administrations of the new formulation should be suitable for therapeutic use.