A method for the determination of cadmium and zinc in geological and environmental materials by radiochemical neutron activation analysis is presented. It is based on the isolation of the analytes using the amphoteric ion exchange resin Retardion 11A8. The elaborated ion exchange procedure is accomplished both before and after neutron activation. Depending on the eluent composition Retardion 11A8 acts as an anion or a cation exchanger. The method was tested by determining Cd and Zn in two reference materials: Lake Sediment (SL-1) and Zinnwaldite ZW-C. The results of quantitative determinations show good agreement with the certified values.