In this study, the relationship between clinical and electrophysiological findings and the timing of the electrophysiological tests in Guillain-Barré syndrome (GBS) were investigated. Electrophysiological abnormalities before and after immunoglobulin G therapy were compared with clinical findings. In 20 patients, the most common early findings were proximal or intermediate conduction block or distal lesion. At 3rd week and thereafter, multipl abnormalities were detected in all patients with functionel scores above 2. After IVIG therapy, all patients but one began to improve while compound muscle action potential amplitudes were found to increase in 4 and to decrease in the other 4. We concluded that electrophysiological findings in GBS has a relationship with clinical findings and with the timing of the electrophysiologic tests. IVIG therapy did not alter the electrophysiological abnormalities despite the appearance of clinical improvement.