The essay proposes a framework that links offenders, target regions, and target sites. In this model, at least three levels of target selection occur: neighborhoods or regions, street blocks, and specific sites. Offenders weigh information on neighborhoods' physical characteristics, such as ease of entry and exit, number of internal boundaries limiting ease of circulation, and signs of guardianship or of incivilities. This framework provides a typology for evaluating research on environmental design and crime prevention, especially defensible space theory, territorial perspectives, and the thesis that neighborhoods or regions, street blocks, and specific sites. Offenders weigh information on neighborhoods' physical characteristics, such as ease of entry and exit, number of internal boundaries limiting ease of circulation, and signs of guardianship or of incivilities. This framework provides a typology for evaluating research on environmental design and crime prevention, especially defensible space theory, territorial perspectives, and the thesis that offenders consider social and physical incivilities when choosing targets. The paper reviews studies which examined relationships between environmental design and crime in Atlanta, Ga; Baltimore, Md.; and Hartford, Conn. This research agrees on one important point: simple effects of physical environment on crime range from small to moderate. Available research suggests that crime prevention efforts should be directed at the street block rather than the neighborhood level of analysis. Diagrams and over 60 references (Author abstract modified)