Behavioral problems such as disinhibition, irritability, restlessness, distractibility, and aggression are common after acquired brain injury (ABI). The persistence and severity of these problems impair the brain-injured individual's reintegration into family, school, and community life. Since the early 1980s, behavior analysis and therapy have been used to address the behavioral sequelae of ABI. These interventions are based on principles of learning and behavior that have been robustly successful when applied across a broad range of other clinical populations. Most of the research on behavioral treatment after ABI has involved clinical case studies or studies employing single-subject experimental designs across a series of cases. The literature supports the effectiveness of these interventions across ages, injury severities, and stages of recovery after ABI. Recommended guidelines for behavior management include: direct behavioral observations, systematic assessment of environmental and within-patient variables associated with aberrant behavior, antecedent management to minimize the probability of aberrant behavior, provision of functionally equivalent alternative means of controlling the environment, and differential reinforcement to shape positive behavior and coping strategies while not inadvertently shaping emergent, disruptive sequelae. This package of interventions requires direction by a highly skilled behavioral psychologist or therapist who systematically monitors target behavior to evaluate progress and guide treatment decisions. A coordinated multisite effort is needed to design intervention protocols that can be studied prospectively in randomized controlled trials. However, there will continue to be an important role for single subject experimental design for studying the results of individualized interventions and obtaining pilot data to guide subsequent randomized controlled trails.