Data from 3,946 nursing homes (66% response rate) were used to examine the advantages and disadvantages of using agency staff. A conceptual model showing potential reasons for the relationship between agency use and care quality was also developed. Fifty-nine percent of nursing homes used some agency staff (i.e., RNs, licensed practical nurses, nurse aides) in 2006. The conceptual model and empirical analyses show that agency staff likely influence other staff, facility operations, and residents. Administrators listed more disadvantages than advantages of using agency staff.