This paper analyzes the relationship between crime and agglomeration where the land, labor, product, and crime markets are endogenously determined. Our main theoretical findings are the following: (i) better accessibility to jobs decreases crime in the short run but may increase crime in the long run; (ii) the per-capita crime rate increases with city size; (iii) when allowing for endogenous policing, lower commuting costs make the impact of police on crime more efficient.