This paper draws on theories from organizational analysis, human resource management, and economics to examine the factors that facilitate or impede employers' use of temporary workers. The results show that temporaries are used to achieve staffing flexibility; they are used more by firms which face union pressure; and they are more likely to be used to buffer regular employees against job loss. On the other hand, temporaries are less likely to be employed in jobs where labor costs are high; and they appear not to be used to obtain specialized services.