The purpose of this study was to investigate the effect of endosulfan on the isolated sciatic nerve of the frog. The nerve was exposed to 0.5 ppm endosulfan for 60 min and then compound action potentials were recorded extracellulary. The latencies, amplitudes, durations of depolarization and repolarization and threshold voltage were measured (n=30). Conduction velocities were calculated using the nerve lengths and latency values of each nerve. It was observed that values of amplitude and duration of repolarization were significantly higher (p