PURPOSE: Improper storage, use, and disposal of prescribed opioids can lead to diversion or accidental poisoning. Our objective was to determine the patterns of storage, utilization, and disposal of opioids among cancer outpatients. PATIENTS AND METHODS: We surveyed 300 adult cancer outpatients receiving opioids in our supportive care center and collected information regarding opioid use, storage, and disposal, along with scores on the CAGE (cut down, annoyed, guilty, eye-opener) alcoholism screening questionnaire. Unsafe use was defined as sharing or losing opioids; unsafe storage was defined as storing opioids in plain sight. RESULTS: The median age was 57 years. CAGE was positive in 58 of 300 patients (19%), and 26 (9%) had a history of illicit drug use. Fifty-six (19%) stored opioids in plain sight, 208 (69%) kept opioids hidden but unlocked, and only 28 (9%) locked their opioids. CAGE-positive patients (p = .007) and those with a history of illicit drug use (p = .0002) or smoking (p = .03) were more likely to lock their opioids. Seventy-eight (26%) reported unsafe use by sharing (9%) or losing (17%) their opioids. Patients who were never married or single (odds ratio: 2.92; 95% confidence interval: 1.48-5.77; p = .006), were CAGE positive (40% vs. 21%; p = .003), or had a history of illicit drug use (42% vs. 23%; p = .031) were more likely to use opioids unsafely. Overall, 223 of 300 patients (74%) were unaware of proper opioid disposal methods, and 138 (46%) had unused opioids at home. CONCLUSION: A large proportion of cancer patients improperly and unsafely use, store, and dispose of opioids, highlighting the need for establishment of easily accessed patient education and drug take-back programs.