A randomised, multicentre study on idebenone vs. oxiracetam was carried out in order to evaluate the therapeutic efficacy of idebenone in subjects with senile cognitive decline. Seventy-nine patients were enrolled: 39 treated with idebenone 45 mg twice daily p.o. and 40 treated with oxiracetam 800 mg twice daily p.o. Idebenone proved to be more effective and was shown to be statistically significant in the following tests: SCAG, Rey's 15 Words, Gottfries Rating Scale. The greater efficacy of idebenone was confirmed by the efficacy judgement given by the investigators. The tolerability of both treatments can be said to be most satisfactory; none of the patients left the study because of side-effects. No significant variations were observed in the vital sips.