This article describes the extent and degree of use of agency staff by nursing homes and examines the relationship between agency staffing levels and quality of care in a large sample of nursing homes (N = 3,876). The quality indicators came from the Nursing Home Compare Web site. It was found that many nursing homes used agency staff (approximately 60% used at least some), and a strong association between better quality and lower agency use existed for both nurse aides and RNs. The influence on quality for the highest levels of agency use, compared with no agency use, was clinically significant. On the basis of these findings, facilities considering using high levels of agency staff should do so carefully.