Based on the suggestion that nerve growth factor plays a core role in the brain maturation process, which is altered in Rett syndrome, we investigate the influence of Cerebrolysin--the brain-derived peptidergic drug - on motor and higher cortical functions in Rett syndrome girls. The open pilot study was performed on nine Rett syndrome girls (aged from 2 years and 2 months to 7 years and 6 months) at stage 3 of the illness, and included both clinical and quantitative EEG evaluations before and after Cerebrolysin treatment. After Cerebrolysin treatment, increases in the behavioral activity, attention level, motor functions, and non-verbal social communication have been shown in Rett syndrome patients. EEG parameters after Cerebrolysin treatment also changed towards normal values, indicating an improvement of the brain functional state. EEG changes included: decrease of theta activity over all cortical regions, increase of beta activity in the frequency band 13-15 Hz, and some restoration of the occipital alpha rhythm (in the narrow 8-9 Hz band). The data obtained suggested possible perspectives of Cerebrolysin in complex therapy of Rett syndrome.