In the past 10 years, many researchers have examined relationships between hospital staffing and patients' risk of health care-associated infection (HAI). To gain understanding of this evidence base, a systematic review was conducted, and 42 articles were audited. The most common infection studied was bloodstream infection (n=18; 43%). The majority of researchers examined nurse staffing (n=38; 90%); of these, only 7 (18%) did not find a statistically significant association between nurse staffing variable(s) and HAI rates. Use of nonpermanent staff was associated with increased rates of HAI in 4 studies (P<.05). Three studies addressed infection control professional staffing with mixed results. Physician staffing was not found to be associated with patients' HAI risk (n=2). The methods employed and operational definitions used for both staffing and HAI varied; despite this variability, trends were apparent. Research characterizing effective staffing for infection control departments is needed.