Passive sampling is a method that can conveniently be used for monitoring of organic contaminants in the aquatic environment comprising its various compartments. The time-integrating properties of passive sampling in combination with the application of a sampling matrix (polymers) with well-defined and constant properties make it possible to achieve a lower inherent variability of exposure information compared to traditional whole water grab sampling. This chapter provides a practical guidance on the selection and use of passive samplers for monitoring organic contaminants in the aquatic environment that should assist users of passive samplers who wish to implement passive sampling methods in their research or monitoring work according to the state of the art. It outlines principles of passive sampling, sampler preparation, field deployment, laboratory processing for chemical and toxicological analysis, calculation of aqueous concentrations and associated uncertainty considerations. Aspects of quality assurance are also addressed.