This document contains details on the sampling of domestic and industrial waste water, i.e. the design of sampling programmes and techniques for the collection of samples. It covers waste water in all its forms, i.e. industrial waste water, radioactive waste water, cooling water, raw and treated domestic waste water. It deals with various sampling techniques used and the rules to be applied so as to ensure the samples are representative. Sampling of accidental spillages is not included, although the methods described in certain cases may also be applicable to spillages.