The medical septal area (MSA) provides the major cholinergic projection to the hippocampus which is critical for function of the memory. Different brain areas through the MSA modulate septohippocampal functions. This study was designed to determin origins of inputs to this area. For this purpose, stereotaxic injections of one microliter HRP (25 percent, Sigma) by Hamilton syringe to the medical septal area were performed in 8 rats. Following brain tissue fixation, sectioning and enzyme histochemical reaction, the labeled neurons were detected microscopically. Retrogradely labeled perikarya observed ipsilaterally in diagonal band of Broca, lateral septum, hippocampus, subfornical area and ventral pallidum in the telencephalon, lateral preoptic area, lateral hipothalamicarea/tuber cinereum, posterior hypothalamus, submammillothalamic, supramammillary and lateral mammillary nuclei in the diencephalons, ventral tegmental area, interpeduncular nucleus, central grey area and locus coerruleus and also bilaterally in raphe nuclei of the brain stem regions. Based on this results, in addition to learning processes, MSA through its connections with subfornical and lateral hypothalamic area can also support the physiological mechanisms for dipsogenic, electrolytic, and pressor responses in living animals.