We examined the efficacy of long-term L-carnitine administration for the treatment of heart failure caused by dilated cardiomyopathy in adult patients. To accomplish this, we studied 80 patients with moderate to severe heart failure (New York Heart Association classification III to IV) caused by dilated cardiomyopathy. This article reports on the nearly 3 years of follow-up data on patient mortality. Primary results will be published in the future. After a period of stable cardiac function up to 3 months, patients were randomly assigned to receive either L-carnitine (2 g/d orally) or placebo. There were no statistical differences between the 2 groups at baseline examination in clinical and hemodynamic parameters, such as ejection fraction, Weber classification, maximal time of cardiopulmonary exercise test, peak VO(2) consumption, arterial and pulmonary blood pressure, and cardiac output. After a mean of 33.7 +/- 11.8 months of follow-up (range 10 to 54 months), 70 patients were in the study: 33 in the placebo group and 37 in the L-carnitine group. At the time of analysis, 63 patients were alive. There were 6 deaths in the placebo group and 1 death in the L-carnitine group. Survival analysis with the Kaplan-Meier method showed that patients' survival was statistically significant (P <.04) in favor of the L-carnitine group. L-carnitine appears to possess considerable potential for the long-term treatment of patients with heart failure attributable to dilated cardiomyopathy.