The performance of patients with myasthenia gravis (MG) on selective neuropsychological tests was examined to assess the diagnostic applicability of such examinations. Twenty-seven patients with MG and twenty-seven age, sex, and education-matched controls were given a battery of tests designed to assess cognitive functions. The MG group displayed significantly lower scores on Mini-mental state test and memory tests. The results indicated that MG patients had cognitive impairment. Results are also discussed with respect to the involvement of cholinergic pathways in the central nervous system.