Large lesions of the septal region in the rabbit increased tonic immobility as measured by the number of successful inductions and by duration of immobility. Open field activity was also increased. Septally lesioned rabbits also exhibited increased emotionality, although the topography of the ''septal syndrome'' in these rabbits was different from that described for rats. The septally lesioned rabbits exhibited increases in fear reactions such as thumping, escape responses and vocalization when caught, rather than increased aggressiveness. The results are discussed in terms of loss of inhibition of species-typical responses after septal damage.