A study was performed in which both anterograde ([3H]leucine radioautography) and retrograde (horseradish peroxidase (HRP) histochemistry) tracing methods were employed to identify the origin of the fimbrial projection to the nucleus accumbens in the rat. The data reveal that this pathway arises predominantly from layers II--III of the anterior two-thirds of entorhinal cortex rather than from any part of hippocampal formation.