The essential role of coenzyme Q--ubiquinone--in biological energy transduction is well established. Reduced Q--ubiquinol--has also been shown to act as an antioxidant and to decrease the action of free radicals, which in turn could cause damage to structural lipids or proteins. The accumulation of lipopigments during aging in several peripheral organs and in the nervous system is considered to be related to the peroxidation of unsaturated fatty acids. An age-related decline of Q-10 has been suggested to occur in man and rats. In this study we followed the effects of life-long oral supplementation of coenzyme Q-10 on the development and life-span and pigment accumulation in peripheral tissues and the nervous system of laboratory rats. The Q-10 supplemented group showed a significant increase in Q-10 in plasma and liver, while it was unchanged in other tissues. There was no significant difference between the two groups in the development and mortality of the animals. No differences were observed in lipopigment accumulation. Our results indicate that in rats, life-long supplementation of Q-10 has no beneficial effects on life-span or pigment accumulation.