OBJECTIVE We sought to construct a valid and reliable patient-reported outcome measure for patients with advanced malignancy and GIO. BACKGROUND Bowel obstruction is the most common indication for palliative surgical consultation in patients with advanced cancer; however, no validated patient-reported outcome measures exist for this population. METHODS A total of 125 patients with GIO and 64 patients without GIO who underwent palliative surgical consultation completed the MDASI-GIO questionnaire and a single global quality-of-life question. Summary statistics were used to assess the symptom burden of GIO patients. Outcome measures were validity (construct and criterion) and reliability (internal and test-retest) for the MDASI-GIO. RESULTS The majority of patients rated the severity of each of the 5 following GIO-specific symptoms as moderate to severe (rating of ≥5 on a 0 to 10 scale): "being unable to eat" (72%), "being unable to have a bowel movement" (65%), "abdominal discomfort" (62%), "stomach feeling full" (55%), and "abdominal cramping" (54%). The MDASI-GIO subscale Cronbach coefficient alpha values were 0.80-0.91, and intraclass correlations were 0.72-0.84. Correlations between MDASI-GIO subscales and global quality of life were -0.39 to -0.49 (P < 0.001 for all comparisons). GIO patients had significantly worse symptoms and higher interference than did non-GIO patients (all P < 0.05) with effect-size differences of ≥0.36, supporting known-group validity. CONCLUSIONS The MDASI-GIO shows initial validity and reliability for assessing the severity of symptoms of patients with GIO and the interference of these symptoms in patients' daily functioning.