The aim of this study was to evaluate the efficacy and tolerability of L-acetylcarnitine therapy in the senile brain. The trial was conducted on a double-blind basis, with a total of 40 patients divided into two groups of 20, treated for 40 days with L-acetylcarnitine and placebo, respectively--the therapeutic regimen being two 500 mg tablets t.i.d. Mental parameters of the senile brain were assessed at 0, 20 and 40 days of treatment, while basal and final values were recorded for a number of laboratory tests. Statistical analysis of results confirmed that short-term, intensive L-acetylcarnitine treatment can determine a significant improvement of the main mental parameters of the senile brain, without incidence of significant side effects.