Cerebrospinal fluid (CSF) concentration of beta-endorphin (beta-Ep), homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA) was measured in 15 patients with dementia of the Alzheimer type (DAT) and in 16 patients suspected of having Binswanger's disease (BD) by MRI, which sometimes resembles DAT clinically. These were classified into three stages according to severity of dementia, Stage 1 (mild dementia)-Stage 3 (severe dementia). CSF levels of HVA decreased significantly in severe dementia, but the level of 5-HIAA did not correlate with dementia severity in both dementia groups. beta-Ep levels did not differ significantly between any stages of DAT, and among controls. beta-Ep levels, however, in BD Stage 1 (27.5 +/- 5.9 pg/ml) were significantly higher (p less than 0.05), but level in Stage 3 (6.7 +/- 2.0) was significantly lower (p less than 0.001) than in the controls (19.2 +/- 4.5). These results suggest that CSF beta-Ep may depend on the cause of dementia rather than severity of dementia, and could possibly distinguish the closely resembling BD from true DAT.