Studies of the costings of crime often sidestep the issue of what constitutes "crime." This is problematic both because it fails to render explicit the policy significance of the categories of offences used in the costings exercise and because, within international and comparative contexts, differences between national definitions may give rise to misleading conclusions. In this paper we elaborate on these problems, indicating the possibilities for resolving them, thus facilitating the evaluation of the costs of crime and enabling more reliable interpretations to be placed on such evaluations. After some general observations on legal definitions of crime, we consider in turn the descriptive definitions used in criminal codes and, external to legislation, by the courts and the police. We continue by briefly considering the relevance of prescriptive definitions for crime costings. We then conclude with some indications on how the definition problem may impact on the costings of crime. References (Published Abstract)