OBJECTIVE:Investigate the prevalence, comorbidities, and correlates of challenging behaviors among clients of the New South Wales Brain Injury Rehabilitation Program. SETTING:All community-based rehabilitation services of the statewide program. PARTICIPANTS:Five hundred seven active clients with severe traumatic brain injury. DESIGN:Prospective multicenter study. MAIN MEASURES:Eighty-eight clinicians from the 11 services rated clients on the Overt Behaviour Scale, Disability Rating Scale, Sydney Psychosocial Reintegration Scale-2, Care and Needs Scale, and Health of the Nation Outcome Scale-Acquired Brain Injury. RESULTS:Overall prevalence rate of challenging behaviors was 54%. Inappropriate social behavior (33.3%), aggression (31.9%), and adynamia (23.1%) were the 3 most common individual behaviors, with 35.5% of the sample displaying more than 1 challenging behavior. Significant associations were found between increasing levels of challenging behavior and longer duration of posttraumatic amnesia, increasing functional disability, greater restrictions in participation, increased support needs, and greater degrees of psychiatric disturbance, respectively (P < 0.004). Multivariate binomial logistic regression found that premorbid alcohol abuse, postinjury restrictions in participation, and higher levels of postinjury psychiatric disturbance were independent predictors of challenging behavior. CONCLUSIONS:Challenging behaviors are widespread among community-dwelling adults with severe traumatic brain injury. Services need to deliver integrated anger management, social skills, and motivational treatments.