The article presents the analytical framework, sets out the cost of crime to potential victims, analyzes equilibrium security expenditures, and identifies factors that determine whether additional security will divert or deter criminals. The results show that security expenditures are strategic complements; if one potential victim implements additional security measures, others will spend more as well. The findings also demonstrate that the more valuable the property at risk or the more easily potential criminals can find other victims, the more likely it is that security expenditures will divert rather than deter crime. 2 figures, 18 notes, 18 references, and 1 appendix