Memory performance, central monoaminergic function and sympathetic nerve activity were studied in patients with dementia of the Alzheimer type (DAT) or with multi-infarct dementia before and after 4 weeks with single or combined drug therapy (choline-piracetam). Analysis of the levels of 3-methoxy-4-hydroxyphenylglycol (MHPG), 3-methoxy-4-hydroxyphenylacetic acid (HVA) and 5-hydroxyindolacetic acid in the cerebrospinal fluid (CSF) and also in urine (plus 3-methoxy-4-hydroxy mandelic acid) showed that the basal values of HVA in the CSF and urine were lower in the more severely demented compared with the mildly demented subjects in both groups. The combined drug treatment resulted in a statistically significant increase in the MHPG level in the CSF of mildly demented subjects of the DAT group, while it seemed not to influence the other monoamine metabolites. The sympathetic nerve activity was similar in both patient groups and was unchanged after therapy. These findings suggest a dopaminergic deficit in advanced stages of the disease and a possible enhancement of the central noradrenergic output with therapy. No effects of therapy on memory performance or correlations between monoamine levels and memory test scores were noted.