Background: Stroke is the leading cause of disability in the United States. Physical therapists treating patients post acute stroke use measurement tools specifically designed to measure gait and balance ability. People with sub-acute stroke typically have rapid and large changes in gait and balance ability while undergoing inpatient physical therapy. There is a lack of information about how much change in gait speed is needed in hospitalized people with sub-acute stroke to be considered an important amount. There is no information regarding the validity, and reliability of the Tinetti Performance Oriented Mobility Assessment (POMA) to measure balance ability in people with stroke or how much change is needed to be important to people in the sub acute phases of stroke. Objective: The purpose of this study was to 1) estimate minimal clinically important difference (MCID) for comfortable gait speed in persons who have experienced stroke and are undergoing inpatient physical therapy using 3 different anchors of change; 2) estimate minimal clinically important difference (MCID) for Tinetti POMA in persons who have experienced stroke and are undergoing inpatient physical therapy using 3 different anchors of change; 3) determine the test retest reliability and minimal detectable change (MDC) for the Tinetti POMA; and 4) explore the construct validity of the Tinetti POMA for use in people with stroke undergoing inpatient physical therapy. Study Design: This study was a prospective, longitudinal study, which followed a cohort of patients who were undergoing inpatient physical therapy post acute stroke. Methods: Participants were recruited if they had a first documented stroke and were receiving physical therapy during inpatient rehabilitation. Participants were excluded from the study if they had a history of a previous stroke, were medically unstable, were non-English speaking or were unable to walk without assistance prior to the current stroke event. Comfortable gait speed measured by a 5-meter walk test, Tinetti POMA scores and motor Functional Independence Measure (FIMTM) scores were collected at admission to and discharge from inpatient rehabilitation. To determine test re-test reliability, two trials of comfortable gait speed were administered during the same treatment session and two trials of Tinetti POMA were performed one day apart. Global Rating of Change (GROC) scores were collected at discharge from inpatient rehabilitation. A score of 6 (¡°a great deal better, an important amount¡±) on a Global Rating of Change scale and achievement of ¡Ý17 point change on the motor FIM was used to dichotomize participants into those who had important change in walking and balance ability and those who did not. Receiver operator characteristic (ROC) curves were constructed to estimate important change values for gait speed using the three anchors. Effect Size (ES) index was used to determine the responsiveness of gait speed and the Tinetti POMA, Intraclass Correlation Coefficient (ICC2,1) was used to determine test re-test reliability and MDC values for gait speed and Tinetti POMA and Spearman¡¯s Rho (rs) was used to explore the construct validity of the Tinetti POMA. Results: The participants in this study were 43 people with average age of 76¡À11 years who had experienced first documented stroke, began inpatient physical therapy at a mean of 8¡À5 days post stroke and were discharged from the hospital at an average of 38¡À11 days post stroke. The mean length of stay for all participants was 23¡À11 days. MCID of comfortable gait speed was estimated to be 0.24 m/s (AUC= 0.644 , sn/sp=66%/64%, LR+=1.83, LR-0.54) anchored to motor FIM change scores. Test re-test reliability of gait speed was ICC2,1=0.931 at admission and ICC2,1=0.987 at discharge. MDC of comfortable gait speed was 0.12 m/s at admission and 0.08 m/s at discharge. MCID of the Tinetti POMA was 7 points (AUC=0.743, sn/sp=79%/64%, LR+=2.18, LR-=0.32) anchored to motor FIM change. Test re-test reliability of the Tinetti POMA was ICC2,1 0.859 and MDC was 5 points. Tinetti POMA scores were moderately correlated to motor FIM and gait speed scores at admission (rs=0.74 and 0.67) and discharge (rs=0.60 and 0.76) to gait speed and motor FIM scores. Conclusions: People with stroke who experience a 7 point change on the Tinetti POMA during inpatient rehabilitation are likely to experience an important change in functional mobility. The Tinetti POMA demonstrates validity and reliability to measure balance ability people with stroke. More research is needed to estimate meaningful change people with sub-acute stroke using larger cohorts with similar characteristics.