Highly purified and metabolically viable gamma-aminobutyric acid (GABA)ergic and cholinergic synaptosomes were prepared from mammalian brain using antisera raised against glutamate decarboxylase and choline acetyltransferase respectively. These antisera appear to recognise specific outwardly facing components of GABAergic and cholinergic synaptic plasma membranes, as well as the specific neurotransmitter-synthesizing enzymes contained within the particular nerve terminal. After cell surface labelling had occurred, synaptosomes were incubated with magnetic microspheres which had previously been coupled with protein A. Labelled synaptosomes were then retrievable in a magnetic field. This separation technique allowed mg quantities of purified-synaptosomes to be prepared which contained less than 2% non-specific contaminants.