This paper extends the labor segmentation perspective on unequal job access. Analyzed here are Census data on the occupational mobility of low-paid workers during the period 1965 to 1970. Upward mobility, defined as movement from a low-paid to a mainstream stratum, is far more common for white men than for women and blacks-even after controlling for differences in age, education, and type of low-paid job. A worker's particular low-paid occupation also strongly affects chances of entering the mainstream stratum. The dominant paradigm for quantitative research on social stratification is questioned, and social policies are suggested.