Are internal migrant workers who have contributed so much to contemporary Chinese economic growth forming a distinct, impoverished underclass (Chan, 2010; Solinger, 2006) or are they slowly merging into the Chinese working class? In this article sociological theory is employed to develop the distinction between underclass and working class, including the conditions and criteria that enable these social categories to be distinguished theoretically and empirically. Drawing on a large range of survey data, including our own analysis of a recent Chinese migrant worker survey, we examine relevant aspects of work and city experience in order to assess the underclass thesis. In addition, we evaluate the argument that younger migrant workers are significantly different in work orientation and strategies for work-life improvement compared with their more experienced counterparts. We conclude that evidence for the underclass thesis is less compelling than an interpretation that views most migrant workers as transitioning into the working class. In addition, although younger workers are more intrinsically oriented than older migrants, both groups concur that labor law enforcement is critical for work-life improvement while simultaneously developing their own collective capacity to influence labor relations outcomes.