Trimethyltin exerts a unique and selective pattern of toxicity which may be related to the neurochemical innervation of the hippocampus. Rats were chronically administered trimethyltin and the kinetics of neurotransmitter uptake was assessed in hippocampal synaptosomes. Additional rats were prepared for histological examination. Uptake of the endogenous hippocampal amino acid neurotransmitters glutamic acid and gamma-aminobutyric acid showed dose-dependent alterations. Uptake of norepinephrine was not significantly affected. Histopathological analysis indicated differential neuronal loss within classically defined hippocampal cell fields.