More and more U.S. workers are counted as employees of firms that they do not actually work for. Among such workers are those who staffed by temporary help service (THS) agencies and leased employees who are on the payroll of professional employment organizations (PEOs) but work for PEOs’ client firms. While several papers study firms’ use of THS services, few examine firms’ use of PEO services. In this article, we summarize PEOs’ business practices and examine how the intensity of their use varies across industries, geographic areas, and establishment characteristics using both public and confidential data.