Objective. The study was undertaken in order to evaluate the effect of magnesium (Mg) supplementation on muscle contents of Mg, muscle strength, muscle mass and sodium, potassium pumps (Na,K- pumps) in patients with alcoholic liver disease. Retrospectively, patients were also stratified according to spironolactone treatment. Material and methods. The study comprised a placebo- controlled, randomized trial in which 59 consecutive patients with alcoholic liver disease were treated with Mg intravenously and orally (12.5 mmol daily) or placebo for 6 weeks. Muscle content of Mg, maximum isokinetic muscle strength, skeletal muscle mass and muscle content of Na,K- pumps were measured before and after Mg supplementation. Results. Muscle Mg did not increase during the trial (paired t- test), but Mg supplementation and the duration of prestudy spironolactone treatment were independent predictors of muscle Mg (multiple regression). Muscle strength increased by 14% during the trial (p < 0.001) and muscle mass increased by 11% (p =.05), but with no difference between placebo and Mg treatment. Spironolactone treatment was associated with a 33% increase in the content of Na,K- pumps (p < 0.001). Conclusions. Six weeks of Mg supplementation did not increase muscle Mg, although Mg supplementation and spironolactone treatment were independent predictors of muscle Mg. The intervention had no effect on muscle strength and mass, but both increased during the study, probably owing to the general care and attendance to the patients. Objective. The study was undertaken in order to evaluate the effect of magnesium (Mg) supplementation on muscle contents of Mg, muscle strength, muscle mass and sodium, potassium pumps (Na, K- pumps) in patients with alcoholic liver disease. Retrospectively, Patients were also stratified according to spironolactone treatment. Material and methods. The study comprised a placebo-controlled, randomized trial in which 59 consecutive patients with alcoholic liver disease were treated with Mg intravenously and orally (12.5 mmol daily) or placebo for 6 weeks. Muscle content of Mg, maximum isokinetic muscle strength, skeletal muscle mass and muscle content of Na, K-pumps were measured before and after Mg supplementation. Results. Muscle Mg did not increase during the trial (paired t-test), but Mg supplementation and the duration of prestudy spironolactone treatment were independent predictors of muscle Mg (multiple regression). Muscle strength increased by 14% during the trial (p <0.001) and Muscle increased by 11% (p = .05), but with no difference between placebo and Mg treatment. Spironolactone treatment was associated with a 33% increase in the content of Na, K- pumps (p <0.001). Conclusions. Six weeks of Mg supplementation did not increase muscle Mg, although Mg supplementation and spironolactone treatment were independent predictors of muscle Mg. The intervention had no effect on muscle strength and mass, but both increased during the study, probably due to the general care and attendance to the patients.