Female Sprague-Dawley rats underwent aspirative lesion of the fimbria to produce septohippocampal disconnection Two weeks after the lesion surgery, fetal septal grafts prepared from ventral forebrain of 13-15 days old fetuses of the same outbred strain were placed into the lesion cavity (grafted group). Three months after grafting, all rats were tested for spontaneous motor activity (SMA), step through passive avoidance (STPA) acid in Morris' water maze (MWM). Six months after grafting, both basal and stimulated acetylcholine (ACh) and choline (Ch) release and their tissue levels were measured in ipsilateral hippocampal slices. Septohippocampal disconnection caused a significant impairment in Morris' water maze tasks, but did not alter spontaneous motor activity and step through passive avoidance. Fimbrial lesion, moreover, also declined both stimulated ACh release and tissue ACh levels in hippocampal slices. While lesion-induced change in Morris' water maze was ameliorated partially, declines in both stimulated ACh release and tissue ACh levels were raised to the control levels by fetal septal graft placed into the lesion cavity. These data show that grafted cholinergic neurons can work biochemically which may not result with a complete behavioral amelioration which is, in fact something more complex.