The forebrain cholinergic system is correlated with learning ability and memory function. Here changes in choline acetyltransferase (ChAT) activities, nerve growth factor (NGF) concentrations and expression of IL-1 beta and IL-6 genes were determined in the basal forebrain, parieto-occipital cortex and hippocampus of hydrocephalic and nonhydrocephalic HTX rats. ChAT activity was remarkably decreased in the parieto-occipital cortex of hydrocephalic animals compared to the other two regions. On the other hand, the NGF concentration in the parieto-occipital cortex was markedly increased during the progression of hydrocephalus compared to the basal forebrain and hippocampus. IL-1 beta and IL-6 m-RNA were detectable only in hydrocephalic HTX rats. The disturbance of uptake and transport of NGF in the affected cerebral cortex is partly related to the psychomotor maldevelopment of congenital hydrocephalic children.