Two groups of 10 patients with Parkinson's disease received doses of either 1g acetyl-L-carnitine (ALC) per day for seven days or 2g. The effects of this drug on intermittent luminous stimulation and on nocturnal sleep patterns were studied. In both cases with either dose of ALC the effect was an improvement of the H response, sleep stages and spindling activity. However a further study of the complexity of action of acetyl-L-carnitine is necessary.