We describe a patient with Guillain-Barré syndrome in whom electrophysiological studies performed 9 days after onset demonstrated multiple focal motor and sensory conduction blocks. Repeat studies 8 weeks later demonstrated complete absence of motor and sensory responses in the arm or leg. These findings suggest that early focal conduction block in sensory nerves might account for sensory symptoms and that there is a spectrum of immune-mediated injury that can proceed from myelin damage to axonal destruction.