An important criminological controversy concerns the proper causal relationships between disorder, informal social control, and crime. The broken windows thesis posits that neighborhood disorder increases crime directly and indirectly by undermining neighborhood informal social control. Theories of collective efficacy argue that the association between neighborhood disorder and crime is spurious because of the confounding variable informal social control. We review the recent empirical research on this question, which uses disparate methods, including field experiments and different models for observational data. To evaluate the causal claims made in these studies, we use a potential outcomes framework of causality. We conclude that, although there is some evidence for both broken windows and informal control theories, there is little consensus in the present research literature. Furthermore, at present, most studies do not establish causality in a strong way.