Electrophysiologic measurements in a 9-year-old girl with tick paralysis demonstrated a prolonged distal latency and a decremental response to 30 Hz stimulation. The nerve conduction determinations became normal after clinical recovery. The pathophysiologic process of this disease seems to be within the peripheral nerve although a central site of action of tick toxin cannot be completely excluded. Tick paralysis should be considered in the individual who develops ascending paralysis.