The efficacy and cost effectiveness of rehabilitation is being closely scrutinized, and demand for cost containment and outcome accountability will most likely increase. Clinically, it has long been believed that timely and appropriate rehabilitation leads to Improved functional recovery in brain-injured individuals. Scientifically, however, controlled studies supporting this belief have been difficult to achieve. Recent credible studies on the benefit of rehabilitation include methods that compare outcomes of patients given rehabilitation versus those not given rehabilitation, different intensities or types of rehabilitation, preversus posttreatment abilities in a nonacute population, and early versus late Initiation of rehabilitation in matched groups. These studies arc reviewed, with commentary on future directions of rehabilitation research