Evaluating transient impairment of consciousness is critical to diagnose epileptic seizures, syncope, para-somnias, organic encephalopathies, and psychogen-ic nonepileptic seizures. Effective evaluation of episodic unconscious events demands interactive interviewing of the patient and witnesses of the events, with judgment as to historians' observational abilities. When generalized tonic-clonic seizures have been witnessed by medical staff or other reliable observers, a search for concomitant nonconvul-sive events and for comorbid illnesses often elucidates diagnoses unsuspected by the referring physician. Consultation for stupor-coma should not miss a potentially reversible acute severe encepha-lopathy, particularly when reversibility requires timely therapy. Perspicacious analyses of complex cognitive-motor phenomena support judicious application of diagnostic procedures, including brief or prolonged EEG and video-EEG, EKG tilt-table testing, EKG loop monitoring, and brain imaging.