Abstract: Disclosed is a method for aiding in the diagnosis of myasthenia gravis. Neostigmine, for example one drop of standard intravenous neostigmine solution (2.5 mg/ml) is instilled into each symptomatic or ptotic eye of patients with suspected or probable myasthenia gravis. The patient is later evaluated for possible changes in ptosis. An observable increase of the palpebral fissure height of at least 2 mm, e.g., after 30-60 minutes after neostigmine instillation is considered to be diagnostic.