• Edrophonium chloride is a cholinergic drug characterized by prompt, brief action on patients with myasthenia gravis. The response consists of temporary increase in muscle strength and general subjective improvement. If the diagnosis has been correct there is no ensuing fasciculation in the muscles and side-effects are minimal. If the subject is psychoneurotic with abnormal fatigability, the effects of the drug can be duplicated by giving a placebo. If the subject is normal, there is usually fasciculation without increase in strength. Excessive doses of the drug elicit false-positive reactions in a small group of hyperreactive subjects. The recommended dosage, based on a study of 300 patients, consists of 2 mg. injected intravenously, to be followed 30 seconds later by an additional 8 mg. if the first portion does not elicit a reaction.