In the present study, electroencephalographic activity of the hippocampus was recorded from free moving rats during operant conditioning. Tone stimuli or photic stimuli were inserted into 20 lever-press responses. The orienting response to novel stimuli was observed 7 of 10 rats at the first test session. Hippocampal rhythmic slow activity (RSA) was presented under Fixed Ratio 20 (FR20) schedule with reinforcements of food pellets and also at the orienting response (OR) . Both RSA frequency of FR and OR was about 8 Hz. We did not find the differences of RSA frequency between two situations. These results indicate that RSA of the hippocampus was associated with the orienting response and with approach behavior to positive reinforcement.