In January 2018, about 17 percent of the workforce in the United States had a part-time job. Part-time employment increased between 1955 and the 1980s as large numbers of women entered the workforce. Since then it has fluctuated in response to rising and falling unemployment. The majority of part-time workers are between 24 and 60 and about two-thirds are women, who often divide their time between work and family. Like other forms of nonstandard work, part-time workers are more likely to have bad jobs, and they are more apt to live in families that are poor, even when controlling for a multitude of labor related variables. Although some part-time jobs offer health and retirement benefits and wages above the poverty threshold, most do not. Only a small share of part-time jobs-between 16 and 17 percent-are located in the primary labor market. When compared to whites, we find that blacks, Hispanic non-citizens, and persons of mixed-race descent are more likely to work part-time. Part-time workers in these groups are also more likely to have jobs in the secondary labor market. Finally, we find that as percentage of part-time workers in occupations increases, the negative effect on job quality associated with the percentage of women in an occupation is greatly reduced or disappear