Symptom occurrence has been shown to predict treatment course and survival in cancer patients. The M. D. Anderson Symptom Inventory-Brain Tumor Module (MDASI-BT) was recently validated as a tool for primary brain tumor patient self-report of symptoms. This study evaluated the reliability and validity of the MDASI-BT in patients with brain metastases. Data collection included demographic and clinical factors, and the MDASI-BT (0-10 scale). Construct validity was assessed using confirmatory factor analysis, and known-group validity was evaluated by detecting group differences due to disease severity and treatment approach. For reliability, Cronbach's alpha values were computed for each subscale. A sample of 124 patients participated, of which 53.2% were women. Participants were primarily white (79.8%) and married (78.2%), and a variety of solid tumor malignancies were represented. Factor analysis revealed six underlying constructs, including affective symptoms, cognitive dysfunction, focal neurologic deficits, constitutional and gastrointestinal symptoms, and interference with life. The solution with these factors explained 68.4% of the variance. Mean symptom scores were 1.2 and 2.6, and mean interference scores were 1.8 and 4.3 for patients with good and poor Karnofsky scores, respectively (P<0.001). These subscales were also sensitive to opioid analgesic use, with group differences of 1.5 and 2.2 (P<0.001). Cronbach's alpha was 0.9 for each of the two subscales. Fatigue, sleep disturbance, drowsiness, distress, and dry mouth were the most severe symptoms. The MDASI-BT demonstrated validity and reliability in brain metastases patients and can be used to identify and monitor symptom occurrence in relation to treatment course and survival.