We reviewed our electrodiagnostic studies of thirty three patients with clinical diagnosis of Guillain-Barr syndrome during the first one month of onset.

1) Positive findings in electrodiagnostic study were more frequent in a group of patients with severe clinical symptoms (p＜0.025).

2) Positive findings were more frequent in tibial F-wave study than conventional tibial nerve conduction study (p＜0.05).

3) Positive findings were more frequent in conduction study of sensory nerves than that of motor nerves (p＜0.05).

4) Positive electrodiagnostic study showing abnormalities in more than one parameter was noted in 87.9% of patients.