Are government employees lazier than private-sector employees? Drawing from theories of work motivation and public service motivation, this article examines three public-private differences that might produce different levels of work effort in the two sectors. First, government and business may offer different extrinsic and intrinsic rewards. Second, public and private workers may seek different rewards. Third, public and private workers may differ in personal characteristics that predict work effort. Using 1989 and 1998 data from the General Social Survey, we find that government employees reported slightly higher work effort than those in the private sector Public- and private-sector workers differ in the value they place on extrinsic and intrinsic motivators, in the rewards their jobs offer and in some personal characteristics. Government jobs offering interesting work and opportunities to help others, combined with the greater age of public employees, explain most of the sectoral differences in self-reported work effort.