Protein concentration and acetylcholinesterase (AChE) and butyrylcholinesterase (BCHE) activities were assayed in the cerebrospinal fluid (CSF) of 26 healthy normal subjects (20-86 years old), 27 patients with dementia of the Alzheimer type (DAT), and 10 patients with dementia of the Alzheimer type with extrapyramidal signs (EDAT). Scores of some of the neuropsychological tests associated with memory and attention were correlated with both plasma and CSF AChE and BuChE inhibition for up to 6 months. Pretreatment with wild-type BChE or A328W tetramers at a dose of 2.8 units/g i.p. reduced cocaine-induced locomotor activity by 50 and 80%.