Fourty-nine patients were examined with epileptic seizures and values of serum and erythrocyte magnesium (sMg, RBC Mg) and serum zinc (sZn) were determined. Chronic deficiency in RBC Mg and sZn were confirmed. The percentage of patients with decreased RBC Mg increased with the time of antiepileptic treatment; significant lowering occurs after 5 years of treatment for RBC Mg and within 5 years for sZn. Various antiepileptics and their combinations have different effects on the degree of the lowering. The therapy of magnesium lactate produces significantly higher RBC Mg and sZn. The clinical, electroencephalographical and biochemical findings are improved.