Abstract: For the therapy of neurological complications in AIDS sufferers, the use of pharmaceutical compositions containing as an active principle at least one compound selected from the group consisting of S-adenosyl-L-methionine salt, 5-methyl-tetrahydro-folic acid, 5-formyltetrahydro-folic acid, when the active principle consists of S-adenosyl-L-methionine and of a derivative of tetrahydro folic acid, the weight ratio between the S-adenosyl-L-methionine salt and 5-methyltetrahydrofolic acid or 5-formyl-tetrahydrofolic acid is comprised between 10/1 and 4/1, in pharmaceutical form, suitable for oral or parenteral administration.