We studied the response properties of interneurons of the dentate gyrus to stimulation of the commissural and perforant path inputs in urethane-anesthetized rats. Commissural stimulation inhibited the population spike evoked by concurrent stimulation of the perforant path. Stimulation thresholds of the interneurons were significantly lower than thresholds of the projection cells. The latency of 3 interneurons was shorter than the onset of the commissurally evoked field response. The results suggest that commissural fibers directly excite interneurons of the dentate gyrus, and the activity of the projection cells may be inhibited in a feed-forward manner.