Viral encephalitis is often followed by cognitive sequelae including intellectual decline whose pathophysiology remains obscure till date. Based on recent laboratory studies implicating the cholinergic system in viral encephalitis, the authors postulate the hypothesis that cholinergic deficit might account for some of the cognitive sequelae in at least some types of viral encephalitis, which might be benefited by central acetyl cholinesterase inhibitors. The case of an adolescent with postencephalitic intellectual decline responding robustly to donepezil is presented.