OBJECTIVES: To evaluate the reliability and validity of the Lupus Impact Tracker (LIT), a patient-based assessment of systemic lupus erythematosus (SLE) disease impact. METHODS: Reliability and validity of scale scores using the 10 selected LIT items were evaluated using two datasets (cross-sectional, n=253 and longitudinal, n=307) which collected information on quality of life (SF-36), disease activity (SLEDAI total score, revised SELENA flare index) and patients’ overall general health rating (GHR) from LupusPRO©.  Internal consistency reliability (ICR) was estimated in both studies using Cronbach’s alpha.  In the longitudinal dataset, reliability was also evaluated by computing the intra-class correlation between LIT scale scores at baseline and follow-up. Convergent validity was evaluated by correlating LIT scale score with SF-36, disease activity and GHR.  Construct validity was examined by known-groups validity (comparing mean scale scores across groups known to differ on conceptually related criterion measures).  Analysis of variance was conducted to compare LIT scale scores across patients stratified by each criterion measure. Responsiveness was studied using known-groups validity.  Specifically, the magnitude and direction of mean score changes on the LIT scale against changes in GHR (0-100 scale) were evaluated. RESULTS: The 10 LIT items (concentration, medication side effects, fulfilling family responsibilities, woke up feeling worn out, pain and aching in body, limited activities due to pain/fatigue, anxiety, depression, self conscious about appearance, ability to plan activities) showed good ICR (0.89) and test-retest reliability (0.87). LIT items correlated moderately (r>0.5) with SF-36 domains and summary measures and the GHR. Mean scale scores differed significantly (p<0.05) in the hypothesized direction across groups stratified by disease activity and GHR.  CONCLUSIONS: The Lupus Impact Tracker, a 10-item PRO, is reliable and valid and offers a practical way of assessing the impact of lupus on a patient’s life.