Cerebrolysin is a peptidergic nootropic drug with a multimodal mechanism of action. It is expected to have a positive influence on neurodegenerative diseases such as senile dementia of the Alzheimer type (SDAT). Experimental studies have shown Cerebrolysin to have a regulatory effect on energy metabolism, a positive influence on behavior through neuromodulation due to its peptide fraction, and most important, a neurotrophic stimulation. In SDAT and related disorders the neurotrophic effect of the drug could play a major role and influence the progress of the illness. A placebo-controlled double-blind trial was designed to examine the efficacy of the drug in SDAT. Confirmatory statistics were used for analysis. 120 subjects with mild to moderate dementia according to the Global Deterioration Scale (GDS) were included in the trial. Their performance on the Mini Mental State Examination (MMSE) was between 15 and 25. The diagnosis was substantiated by the Hachinski Ischemic Score and cranial computed tomography. The inclusion and exclusion criteria were formulated so as to prevent a distortion between the two arms by secondary dementia or other disease. The two arms received either placebo or the drug once a day (30 ml Cerebrolysin in 100 ml physiological saline i.v.) from Monday to Friday for four weeks. Physiological saline (130 ml) was used as placebo. Primary variables used for the statistical analysis were the Clinical Global Impression (CGI), which measures the improvement in symptoms, the SCAG score, and the performance in the trial-making test (ZVT-G). The self-assessment in the Bf-S and the activities of daily living in the NAI were used as secondary variables.(ABSTRACT TRUNCATED AT 250 WORDS)