The harmonised Guidance for the Definition of Residue provides a common approach to residue identification of the pesticide and its metabolites. Residue analysis for dietary risk assessment emphasises analysis of the parent compound and its most significant metabolites, taking into consideration both exposure and relative toxicities. Residue analysis for tolerance/MRL enforcement purposes focuses on those 'analytes' which would indicate a possible misuse of the pesticide and which also can be detected and measured by a broad base of national laboratories, i.e., residues which are easy to measure and which occur in large quantities. The Guidance Document on the Definition of Residue balances these concerns so that the appropriate chemical moieties can be analysed. It differentiates residue definitions for data generation and risk assessment purposes versus MRL/tolerance-setting and enforcement purposes. Such guidance will be available to pesticide applicants so that they may propose definitions of residue for each purpose and provide data for implementation.