Purpose: Traditionally, opioids have been the cornerstone of therapy for patients suffering from cancer pain, regardless of the potential to develop opioid tolerance. In chronic pain patients who experience improving pain by opioid rotation, the clinical role of opioid tolerance is gaining more recognition. Case Report: Presented here is the case of a 60-year-old man with recurrent rectal carcinoma with huge pelvic mass and iliac and neck of femur bone metastases, suffering with intractable 9/10 pain on the numerical rating scale in his right hip and leg. In spite of escalating doses of fentanyl to 50.4 μg/72 hours and started gabapentin for adjunctive pain treatments, the patient continued to experience severe pain. The clinical picture suggested the possibility of opioid torelance. We decreased the fentanyl dose and started oxycodone. Opioid rotation to 30 mg/day sustained release oxycodone and withdrawed fentanyl provided effective pain control. The patient's pain level dropped to a more acceptable 2/10. He was more alert, and his pain was tolerable until his death. Conclusion: Opioid tolerance might be considered in a patient who has no evidence of disease progression, who is on clinically reasonable doses of opioids. Opioid rotation may provide a favorable clinical outcome in those patients who have failed to benefit from adjunctive pain treatments. Palliat Care Res 2011; 6(1): 330-335