Eleven patients with presenile Alzheimer type dementia (ATD) were treated with N-terminal ACTH fragments for 14 days. No change in cognitive functions was observed during the treatment. A significant increase in CSF beta-endorphin (beta-EP) levels was found, while ACTH and beta-lipoprotein remain unaffected. The possibility that ACTH and its moieties could interfere with beta-EP activities in CNS is discussed.