The purification of a putative kainic acid receptor has been accomplished by the development of a domoic acid affinity column. Domoic acid, immobilized through the carboxylic acid groups, retains the ability to bind kainic acid receptors in solution. The purified receptor from frog brain migrates as a diffuse band centred at a relative molecular weight of 48,000 on polyacrylamide gels. The availability of a purified receptor preparation has allowed the further molecular characterization of a kainic acid receptor through the production of anti-receptor monoclonal and polyclonal antibodies. Monoclonal antibodies that both immunoprecipitate tritium (3H)-kainic acid binding activity and label the molecular weight (Mr) = 48,000 band on Western blots, provide strong evidence that this band is in fact the ligand binding subunit of a kainic acid receptor in frog brain. The use of these antibodies in immunocytochemical studies has demonstrated that the majority of the kainic acid receptor immunoreactivity is concentrated at extrasynaptic sites on neuronal membranes and that a small percentage of the immunoreactivity is located postsynaptically.