We evaluated the clinical effectiveness of ceruletide in patients with dementia of the Alzheimer type and its effects on neurotransmitters in cerebrospinal fluid. Mini mental state scores were significantly increased after ceruletide administration. Acetylcholinesterase activity in cerebrospinal fluid was significantly increased after administration, while somatostatin and monoamine metabolites showed no significant changes. Ceruletide improved intellectual function, and the improvement seemed to be due to activation of neurotransmitters in the acetylcholine system in the brain. Though the subjects were elderly patients, no side effects presenting clinical problems were observed. This warrants further detailed studies on the effectiveness of ceruletide in dementia of the Alzheimer type.