Immigrants in the United States often live, at least for a time, in neighbourhoods that have high concentrations of fellow immigrants. Typically, these neighbourhoods also have high poverty levels and are located near concentrations of the native-born poor. Conventional wisdom is that living in extremely poor neighbourhoods leads to 'concentration effects' that exacerbate the problems of poverty and limit economic opportunity. While immigrants are not immune to the problems of crime, gangs, dilapidated housing and failing schools associated with high-poverty neighbourhoods, it has been argued that immigrant neighbourhoods provide advantages as well. These include the creation of parallel institutions, vernacular information networks and familiar cultural practices. The analyses presented here provide some support for this notion, by showing immigrants' progress from higher- to lower-poverty neighbourhoods over time. Yet Mexican immigrants do not transition nearly as rapidly, providing support for the segmented assimilation hypothesis.