The ability of midbrain homogenates from two strains of mice to accumulate several putative neurotransmitters, or their precursor in the case of acetylcholine, has been examined. The high-affinity transport mechanisms toward glutamate, GABA, dopamine, and glycine were similar in both strains. The seizure-prone DBA21BG strain had a significantly higher capacity to transport choline than did the relatively seizure-resistant C57BL/6 IBC mice. Howaver, no difference in the density of muscarinic binding sites in the two mouse strains was found.