A multicentre, randomised, controlled study compared the efficacy of l-alpha-glyceryl-phosphorylcholine (alpha GPC) and ST200 (acetyl-l-carnitine) among 126 patients with probable senile dementia of Alzheimer's type (SDAT) of mild to moderate degree. Efficacy was evaluated by means of behavioural scales and psychometric tests. The results showed significant improvements in most neuropsychological parameters in the alpha GPC recipients. Improvements also occurred in the ST200 recipients but to a lesser extent. Tolerability was good in both groups. These positive findings require replication in larger, double-blind, longitudinal studies coupling clinical and biological determinations.