A group of children with neurological diseases was examined, in which in 70-95% (according to age) of children the contents of magnesium in hair and in 39-44% in serum were lowered. The most frequent neurological signs in the relevant group of children were described. A case of a child with hypomagnesemia in whom had been falsely diagnosed and positive therapeutic effects epilepsy were obtained after supplementation with magnesium preparations (Asmag, Magne B6) were presented.