AbstractA recently developed stacked neutron guide system, installed at the Interfaculty Reactor Institute in Delft, The Netherlands, is described. It comprises two 3-m-long stacks of curved narrow neutron guides. This system is designed to transmit thermal neutrons by means of total reflection and, at the same time, attenuate fast neutrons and gamma radiation strongly. Comparison of calculated and measured flux densities shows an excellent transmission of the thermal neutrons. The measured fast neutron and gamma radiation dose-equivalent rates are consistent with the design values.