Partial deafferentation of the hippocampus was obtained by transection of unilateral partial fimbria-fornix. On the seventh postoperational day, there appeared in the lesioned hippocampus respectively a 72.5%, 45.7% and 52.2% reduction in acetylcholine content, choline acetyltransferase and cholinesterase activity. A concomitant 16.3%, 31.1% and 30.3% reduction in noradrenaline, dopamine and serotonin content respectively was also observed, while amino acids content did not show any change. The results indicate that the cholinergic and monoaminergic afferents of the hippocampal formation in the rat reach their target regions via the fimbria-fornix.