Electrodiagnostic study in acute polyradiculoneuropathy is considered as the only objective diagnostic tool in diagnosis and predicting prognosis. Because of the temporal change in electrophysiologic findings and discrepancy in prognostic parameters, it has many limitations in applying it clinically. In order to get the most probable electrodiagnostic parameter for prognosis and suggestive protocol in electrodiagnostic study, 36 patients were analyzed clinically and with standard electrodiagnostic findings. There was no consistent parameter of prognosis throughout time but electrodiagnostic findings studied between 8 weeks and 12 weeks since the onset of the disease were well correlated with clinical features and prognosis. It is suggested that the protocol for electrodiagnostic study in acute polyradiculoneuropathy is the baseline study between 2 weeks and 4 weeks since onset and the F/U study for prognosis between 8 weeks and 12 weeks.