This Technical Report (TR) provides guidance and recommendations regarding the availability and use of radiation sources that are needed when testing and evaluating instruments used for the detection of illicit trafficking of radioactive material. The relevant standards are listed in 4.1. Guidance includes the use of surrogate or replacement radioactive materials that could be more easily obtained. The object of this Technical Report is to provide guidance to instrument manufacturers@ users@ and testing organisations as to the selection and possible use of radiation sources@ source surrogates and source simulation tools when testing and evaluating an instrument's ability to detect and identify illicit trafficking of radioactive material.