During 1982-86, 43/137 patients with cardiomyopathy, Classes II, III and IV, had ejection fractions (EF) below 40%, and a mean EF of 25.1 +/- 10.3%. During treatment of these 43 patients with coenzyme Q10 (CoQ10), EF increased to 41.6 +/- 14.3% (p less than 0.001) over a mean period of 3 months (range, 2-4 months). At four subsequent periods up to 36 months. EF ranged from 43.1 +/- 13.3 to 49.7 +/- 6.4% (each period, p less than 0.001). The mean CoQ10 control blood level was 0.85 +/- 0.26 micrograms/ml which increased on treatment to 1.7 to 2.3 micrograms/ml for five periods up to 36 months (each period, p less than 0.001). The survival rates for all 137 patients treated with CoQ10 and for the 43 patients with EF below 40% were both about 75%/46 months. These two survival rates were comparable between 24 and 46 months, which is of extraordinary significance and importance when compared to survival of about 25%/36 months for 182 patients with EF below 46% on conventional therapy without CoQ10. The improved cardiac function and pronounced increase of survival show that therapy with CoQ10 is remarkably beneficial due to correction of CoQ10 deficiency in mechanisms of bioenergetics.