The electrodiagnostic findings in 48 patients with Guillain-Barré syndrome were retrospectively analyzed to determine the correlation between elecrodiagnostic findings and the functional outcome. Electrodiagnostic protocol included distal motor latency, amplitude, velocity, the degree of conduction block, motor conduction velocity, and fibrillation potential density. Function was evaluated by functional status index proposed by Miller at nadir, 2 months and 6 months after onset. After 6 months, 13 patients were able to walk independently and 6 patients were ambulatory with varying degrees of impairment. The distal motor latency, the degree of conduction block and motor conduction velocity did not correlate significantly to the functional status index, but the mean amplitude of distal compound muscle action potential and fibrillation potential density were found to be powerful predictors of outcome.