Trimethyltin (TMT) apart from causing cholinergic denervation of the hippocampus, damages the serotonergic inputs into the hippocampus as well. In the present study, fetal cholinergic and serotonergic rich neuronal populations from septal and raphe regions, respectively, were transplanted alone or in combination (as co-grafts) in the hippocampus of TMT exposed rats. Neurotransmitter receptor binding and neurotransmitter levels were assayed 6 months post-transplantation. Fetal septal transplants (rich in cholinergic neurons) significantly restored the deficits in cholinergic (muscarinic) receptor binding and acetylcholinesterase activity caused by TMT exposure. Raphe transplants (rich in serotonergic neurons) restored the deficit in serotonergic receptor binding and serotonin levels caused by TMT. Co-grafts of fetal raphe and septal neurons restored both the cholinergic (muscarinic) and serotonergic receptor functions. The results suggest that co-grafting technique could provide a better restoration of functional deficits when more than one type of neuronal population is damaged.