180 Background: There is no standardized and universally accepted pain classification system for the assessment and management of cancer pain in both clinical practice and in research studies. The Edmonton Classification System for Cancer Pain (ECS-CP) is an assessment tool that has demonstrated value in assessing pain characteristics and response. The purpose of the study was to determine the relationship between the negative ECS-CP features and some pain related variables like pain intensity and opioid use. Also, we explored whether the number of negative ECS-CP features was associated with higher pain intensity. Methods: Electronic charts of 100 patients at the outpatient supportive care clinic in a comprehensive cancer center were reviewed for patient characteristics, initial ECS-CP assessment, the morphine equivalent daily dose (MEDD), opioid rotation, the Edmonton Symptom Assessment Score (ESAS), Memorial Delirium Assessment Scale (MDAS), performance status, and the use of adjuvant analgesics. Results: Ninety one out of the 100 charts were therefore eligible for analysis. The median age was 58.4 years. The most common primary cancer site was gastrointestinal cancer (22.1%). The median pain intensity was 6 and the median MEDD was 45mg. Incident pain was the most common ECS-CP feature (60%) and cognitive dysfunction was the least frequent feature (2%). Neuropathic pain was associated with higher median pain intensity (7 vs. 5, p=0.007) and median MEDD requirement (83 vs. 30, p=0.013). Psychological distress was associated with higher median pain intensity (7 vs. 5, p=0.042). Incident pain was also associated with a trend for higher pain intensity (6 vs 5, p= 0.06). A higher number of negative ECS-CP features was associated with higher pain intensity (p=0.01). Conclusions: The ECS-CP was successfully completed in the majority of patients, demonstrating its utility in routine clinical practice. Neuropathic pain and psychological distress were associated with higher pain intensity. Also, neuropathic pain was associated with higher MEDD. A higher sum of negative ECS-CP features was associated with higher pain intensity. Further studies will be needed to explore this observation.