Over the past years, the IAEA has provided support to a number of Member States engaged in the implementation of hydrological projects dealing with the design and monitoring of artificial recharge (AR) systems, primarily situated in arid and semiarid regions. This publication discusses several theoretical aspects important to the understanding, planning and monitoring of AR and aquifer storage and recovery (ASR) schemes and presents a selected number of examples illustrating the usefulness of applying isotopes and other tracers in different phases of AR and ASR. The publication is expected to be of interest to hydrologists and water managers in areas where intensive exploitation of available water resources leads to shortages of water and where AR is being considered or is being implemented.