The European Food Safety Authority, following a request from the European Commission, has published a guidance document for the risk assessment of GM plants and derived food and feed to assist in the implementation of provisions of Regulation (EC) 1829/2003 of the European Parliament and Council on GM food and feed. This regulation has applied since 18 April 2004. In principle, hazard identification and characterisation of GM crops is conducted in four steps: characterisation of the parent crop and any hazards associated with it; characterisation of the transformation process and of the inserted recombinant DNA, including an assessment of the possible production of new fusion proteins or allergens; assessment of the introduced proteins (toxicity, allergenicity) and metabolites; identification of any other targetted and unexpected alterations in the GM crop, including changes in the plant metabolism resulting in compositional changes and assessment of their toxicological, allergenic or nutritional impact. In relation to allergenicity specifically, it is clear that this property of a given protein is not intrinsic and fully predictable but is a biological activity requiring an interaction with individuals with a predisposed genetic background. Allergenicity, therefore, depends on the genetic diversity and variability in atopic human subjects. Given this lack of complete predictability it is necessary to obtain, from several steps in the risk-assessment process, a cumulative body of evidence that minimises any uncertainty about the protein(s) in question.