This book consists of 8 chapters, each being the edited version of invited papers given at a symposium organized by the HPA. The first 4 are devoted to instrumentation, and cover the accuracy required in surveys, the calibration of monitors for dose, dose-rate and contamination and a short evaluation of available health physics instruments. The remaining 4 deal with the practical application of monitoring in real-life situations: with X- and γ-ray installations, environmental monitoring when unsealed sources are used, wipe testing and leak testing and the monitoring of airborne contaminants.