CONTEXT: Little research has been conducted on aggression directed at staff by nursing home residents. OBJECTIVE: To estimate the prevalence of resident-tostaff aggression (RSA) over a 2-week period. DESIGN: Prevalent cohort study. SETTING: Large urban nursing homes. PARTICIPANTS: Population-based sample of 1,552 residents (80 % of eligible residents) and 282 certified nursing assistants. MAIN OUTCOME MEASURES: Measures of resident characteristics and staff reports of physical, verbal, or sexual behaviors directed at staff by residents. RESULTS: The staff response rate was 89 %. Staff reported that 15.6 % of residents directed aggressive behaviors toward them (2.8 % physical, 7.5 % verbal, 0.5 % sexual, and 4.8 % both verbal and physical). The most commonly reported type was verbal (12.4 %), particularly screaming at the certified nursing assistant (9.0 % of residents). Overall, physical aggression toward staff was reported for 7.6 % of residents, the most common being hitting (3.9 % of residents). Aggressive behaviors occurred most commonly in resident rooms (77.2 %) and in the morning (84.3 %), typically during the provision of morning care. In a logistic regression model, three clinical factors were significantly associated with resident-to-staff aggression: greater disordered behavior (OR =6.48, 95 % CI: 4.55, 9.21), affective disturbance (OR=2.29, 95 % CI: 1.68, 3.13), and need for activities of daily living morning assistance (OR= 2.16, 95 % CI: 1.53, 3.05). Hispanic (as contrasted with White) residents were less likely to be identified as aggressors toward staff (OR=0.57, 95 % CI: 0.36, 0.91). CONCLUSION: Resident-to-staff aggression in nursing homes is common, particularly during morning care. A variety of demographic and clinical factors was associated with resident-to-staff aggression; this could serve as the basis for evidence-based interventions. Because RSA may negatively affect the quality of care, resident and staff safety, and staff job satisfaction and turnover, further research is needed to understand its causes and consequences and to develop interventions to mitigate its potential impact.KEY WORDS: nursing home; dementia-related behaviors; elder abuse; staff mistreatment.