A 25-year-old man with essential startle disease has been reported. He had a history of sudden jerks and falls in response to unexpected stimuli. Abnormal falling developed when he learned to walk. No similar cases are known in his family. Physical examination revealed hyperreflexia. Pathologic startle reflex was elicited by light touching on the patient's nose, clapping or making other noises. EEG response to startle stimuli consisted of spikes recorded from both centroparietooccipital regions immediately preceding diffuse muscle and movement artifacts. The motor responses to auditory stimuli, which are startle reflex on the orbicularis oculi, sternocleidomastoid, biceps and quadriceps femoris muscles, habituated within 2-4 trials. Electrical stimulation of the median nerve at the wrist elicited a consistent C reflex (cortical long loop reflex) but not any giant cortical somatosensory evoked potentials.