鈥� We performed a double-blind study of the effect of physostigmine vs saline on the performance of memory and constructional tasks in a patient with probable Alzheimer's disease. On the days of physostigmine administration, a remarkable improvement in copying figures was observed. However, physostigmine administration had only a limited effect on memory performance. The results are interpreted in the context of recent biochemical studies of the brain in Alzheimer's disease, which suggest selective loss in the central cholinergic system.