BACKGROUND:: One challenge in rehabilitation is determining whether improvement in the patient is a treatment-specific effect or due to extraneous factors (eg, the passage of time, spontaneous recovery). DESIGN:: Descriptive, model building, and 2 cases illustrating the model. METHOD:: The Model for Assessing Treatment Effect (MATE) incorporates the conceptual frameworks of the International Classification of Functioning, Disability, and Health (ICF), along with single-case experimental methodology. RESULTS:: The MATE contains 7 levels organized in a hierarchy, representing (i) increasing specificity of evaluation procedures and (ii) control of extraneous variables during therapy. Two illustrative cases of patients with traumatic brain injury undergoing inpatient rehabilitation for, inter alia, cognitive-communication impairments are described to illustrate common clinical practice (level 2 of MATE) and a superior method using a multiple-baseline design across behaviors, enabling rigorous evaluation of treatment effect (level 6 of MATE). CONCLUSIONS:: The MATE offers a systematic, evidence-based approach for implementing ICF-informed goals into clinical practice. It also provides a benchmark against which a clinical service can be evaluated in terms of the rigor of its therapy program.