The projection of the septohippocampal pathway in the rat was studied using anterograde transport of horseradish peroxidase. This technique provides a number of advantages over other methods including the ability to differentiate between terminal and preterminal axon labeling, a very high ‘signal to noise’ ratio, and a short delay in obtaining results. As applied to the septohippocampal projection, anterograde transport of horseradish peroxidase reveals a dense septal input to the dentate hilus and stratum oriens of CA3, a modest input to the dentate molecular layer and stratum radiatum of CA3, and a very sparse input to stratum oriens and stratum lacunosum-moleculare of CA1 with most labeling in this field confined to axons passing through it. In addition, our results suggest that a septal projection to the supragranular region of the dentate is present only within the rostral pole of the hippocampal formation. Potential artifacts such as labeling of fibers-of-passage and ‘collateral’ filling do not appear to interfere with the results but transneuronal transport of horseradish peroxidase may occur when large amounts of the protein are injected.