Assessing the outcomes of physical therapy will be difficult in many instances, because it is difficult to separate the specific contribution of physical therapy from the effects of overall rehabilitative efforts. Nonetheless, more studies are needed to establish what works, both specifically and overall. Appropriate care should be defined on the basis of what has been shown to be effective. In most instances, this knowledge will come from quasi-experimental designs that utilize epidemiological methods. In designing effectiveness studies, careful attention needs to be paid to defining the treatment in terms of type and amount of care. Other factors that will affect the outcome, including baseline performance, risk factors, and environment, must be adequately dealt with in the analysis. Rehabilitation's success depends on the patient's performance in his or her actual living situation, not just in a controlled environment. Blaming the community for failing to provide a supportive environment will not exonerate rehabilitation's responsibility.