There is a commonplace but powerful argument that links the religious resurgence in the Muslim world to the urban ecology of overcrowded slums in the large cities. Poverty and precarious life, together with anomie and lawlessness, condition the dispossessed to embrace ideologies and movements that offer communities of salvation and support while preaching radical politics. This article questions the premises of such arguments in an attempt to nuance the relationship between the urban dispossessed and radical Islam. By examining the politics of slums and militant Islamism in the Middle East, notably Egypt and Iran, I suggest that key to the habitus of the dispossessed is not anomie or extremism but ‘informal life’— one that is characterized by flexibility, pragmatism, negotiation, as well as constant struggle for survival and self-development. The relationship between the urban dispossessed and radical Islamists tends to be both contingent and instrumental.