This paper focuses on the benefits of neuropsychological assessment for evaluating a brain-injured person's functional abilities and rehabilitation needs. The importance of early assessment in addressing these goals is discussed. Strengths and weaknesses of neuropsychological assessment for predicting a person's ability to participate in normal activities of daily living are considered. Test data taken alone often lack ecological validity, but nevertheless, specific test findings can be used to predict functional skills. The ecological validity of neuropsychological testing can be extended by observing the patient's approach to tasks in the assessment environment and by observing the patient in his or her normal activities. Evaluation information obtained by allied rehabilitation professionals, including occupational and speech and language therapies, can be integrated with neuropsychological test data to both extend the generalizability of our findings and to validate hypotheses generated from our test data. The use of neuropsychological test data in planning a cognitive rehabilitation program is also considered.