The present invention is directed to a method of treating a sudden onset of at least one neurological deficit in a subject. The sudden onset of neurological symptoms is an indicator of a possible stroke, also termed a cerebrovascular accident. The method comprises administering an effective amount of melatonin to the subject immediately after the sudden onset of at least one neurological deficit, and preferably within three hours of the sudden onset of the at least one neurological deficit. Preferably, the effective amount of melatonin is at least about 200 mg and less than about 1000 mg, although for a small child or infant the effective amount of melatonin may be less than about 200 mg while for a large adult it may be more than about 1000 mg. It is expected that the effective amount of melatonin is no more than about 1500 mg in almost all cases.