OBJECTIVES: To measure participation outcomes with a computerized adaptive test (CAT) and compare CAT and traditional fixed-length surveys in terms of score agreement, respondent burden, discriminant validity, and responsiveness. DESIGN: Longitudinal, prospective cohort study of patients interviewed approximately 2 weeks after discharge from inpatient rehabilitation and 3 months later. SETTING: Follow-up interviews conducted in patient's home setting. PARTICIPANTS: Adults (N=94) with diagnoses of neurologic, orthopedic, or medically complex conditions. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Participation domains of mobility, domestic life, and community, social, & civic life, measured using a CAT version of the Participation Measure for Postacute Care (PM-PAC-CAT) and a 53-item fixed-length survey (PM-PAC-53). RESULTS: The PM-PAC-CAT showed substantial agreement with PM-PAC-53 scores (intraclass correlation coefficient, model 3,1, .71-.81). On average, the PM-PAC-CAT was completed in 42% of the time and with only 48% of the items as compared with the PM-PAC-53. Both formats discriminated across functional severity groups. The PM-PAC-CAT had modest reductions in sensitivity and responsiveness to patient-reported change over a 3-month interval as compared with the PM-PAC-53. CONCLUSIONS: Although continued evaluation is warranted, accurate estimates of participation status and responsiveness to change for group-level analyses can be obtained from CAT administrations, with a sizeable reduction in respondent burden.