The aim of this paper was to observe the projections of NOS positive neurons to the hippocampus from septal area. The projections were retrograde traced by combined method of horseradish peroxidase (HRP) and nicotinamide adenosine dinucleotide phosphate diaphorase (NADPH-d) in rats. After injecting of HRP into the dorsal hippocampus

the ventral hippocampus or the posterior part of hippocampus

the HRP-NOS double labeling neurons were distributed in the medial septal nucleus

the dorsal and ventral parts of ventical limb of diagonal band nucleus. The hippocampus received the projections of NOS positive neurons from the septal area

the number of septo-hippocampal projections of NOS positive neurons were about 1/3 of the total number of septo-hippocampal projections.