The diurnal rhythm organization of drinking behavior was determined prior to and after suprachiasmatic nucleus (SCN) lesions. Five weeks after SCN lesions which produced total loss of the diurnal rhythm, the anterior hypothalamus including the SCN of fetal rats was transplanted into the floor of the 3rd ventricle of the lesioned rats. Eight weeks after the graft, rats recovered their rhythm. The results show that grafts allow animals to recover lost functional properties due to lesions, and further support the notion that the SCN is a pacemaker for certain behaviors.