Over the last ten years we have seen a dramatic increase in the utilization of part-time workers by the United Parcel Service (UPS). This increase has been coupled with a stunningly high turnover rate of 150 percent among these workers. This study documents the deteriorating work environment for part-time workers at UPS and finds that a lack of full-time opportunities, a pervasive pattern of management mistreatment, and an alarmingly high injury rate are the primary determinants of the high turnover rate.