Aim of this study was to evaluate adjuvant magnesium orotate on mortality and clinical symptoms in patients with severe heart failure under optimal cardiovascular medication. In a monocentric, controlled, double-blind study, 79 patients with severe congestive heart failure (NYHA IV) under optimal medical cardiovascular treatment were randomised to receive either magnesium orotate (6000 mg for 1 month, 3000 mg for about 11 months, n=40) or placebo (n=39). Both groups were comparable in demographic data, duration of heart failure and pre- and concomitant treatment. After mean treatment duration of 1 year (magnesium orotate: 364.1+/-14.7 days, placebo: 361.2+/-12.7 days) the survival rate was 75.7% compared to 51.6% under placebo (p<0.05). Clinical symptoms improved in 38.5% of patients under magnesium orotate, whereas they deteriorated in 56.3% of patients under placebo (p<0.001). Magnesium orotate may be used as adjuvant therapy in patients on optimal treatment for severe congestive heart failure, increasing survival rate and improving clinical symptoms and patient's quality of life.