It is suggested that the Harm Principle can be viewed as the moral basis on which genetically modified (GM) food is currently regulated. It is then argued (a) that the concept of harm cannot be specified in such a manner as to render the Harm Principle a plausible political principle, so this principle cannot be used to justify existing regulation; and (b) that even if the Harm Principle were a plausible political principle, it could not be used alone in the regulation of GM food, since it does not express a concern for the expected benefits of such food.