Background: Adequate dosing of analgesics is important for optimum cancer pain control & quality of life (QoL). To understand current attitudes toward analgesic treatment for cancer pain in SEA, the ACE study explored patient & physician satisfaction with pain control in 6 SEA countries. Methods: This cross-sectional observational study included 465 adult outpatients prescribed analgesics for cancer pain for ≥1 month in Indonesia, Malaysia, Philippines, Singapore, Thailand, & Vietnam. Pain intensity, sleep disturbance, QoL, satisfaction with pain control, & physicians’ assessment of adequacy of analgesics were recorded via questionnaires. Current analgesic doses prescribed were extracted from medical records. Results: Most patients (84%) had stage 3 or 4 cancer. While 91% were prescribed opioids, mean reported pain intensity was 4.1 (0/no pain, 10/worst possible pain) & most had problems with sleep (55%) & QoL (problems with pain/discomfort [82%], usual activities [66%] & anxiety/depression [56%]). 60% of patients were satisfied with their pain control status & 30% found it acceptable. Physicians more often reported dissatisfaction with patients’ pain control status compared with patients (21% vs 10%). Patient-physician concordance in satisfaction with pain control was low (weighted Kappa 0.36; 95% CI 0.30-0.43). More than 1 in 4 physicians (29%) assessed prescribed analgesics to be “inadequate” for pain control. Median daily dose prescribed in oral morphine equivalents was 30 mg for both morphine & tramadol. Of the SEA countries included, prescribed doses of opioids were generally lower in Indonesia & higher in Vietnam. Conclusions: The results highlight the complexity of managing cancer pain in SEA. Despite unrelieved pain, sleep disturbance & QoL issues, many patients still reported satisfaction with pain control. Notably, physicians expressed dissatisfaction more frequently than patients. These findings suggest a need for all-round pain status assessment (including pain intensity, sleep disturbance, QoL) & improved patient-physician communication about analgesic treatment expectations, pain control & adverse effects.