Cohen and Felson's (Cohen and Felson American Sociological Review 44 (4):588-608, 1979) routine activity theory posits that for a crime to occur three necessary elements must converge in time and space: motivated offenders, suitable targets, and the absence of capable guardianship. Capable guardians can serve as a key actor in the crime event model; one who can disrupt, either directly or indirectly, the interaction between a motivated offender and a suitable target. This article critically reviews the literature on guardianship for crime prevention. Our specific focus is two-fold: (1) to review the way guardianship has been operationalized and measured, and (2) to review experimental and quasi-experimental evaluations and field tests of guardianship. Research on routine activities has had an uneven focus resulting in the neglect of the guardianship component (Reynald Crime