Coenzyme Q10 (CoQ10) and the opiate antagonist naloxone were compared as to their effect on the survival of mongolian gerbils with unilateral carotid ligation-induced stroke. Without medication all of the stroke gerbils died within 28 hours, but with a subcutaneous implantation of a 10 mg pellet of naloxone, 20% of the gerbils lived for 4 weeks. When a 250 mg pellet of CoQ10 was implanted subcutaneously, a definite effect on survival was observed, with 45% of the stroke gerbils living for 4 weeks. Considering that the action mechanisms of CoQ10 and naloxone are different, the combined use of these drugs in the treatment of stroke needs to be investigated.