This Safety Report provides assistance in the setting up and operation of an indirect monitoring programme for workers. As such it complements Safety Series No. 114, Direct Methods for Measuring Radionuclides in the Human Body (1996). It gives technical advice on the collection and analysis of biological and physical samples used to estimate intakes of radionuclides. The analytical methods described may also be applied to the monitoring of patients following medical treatment or of members of the public following a release of radionuclides to the environment.