We have treated 37 patients with intractable pain (35 with cancer-related pain) by continuous intrathecal morphine infusion via implanted pump. These patients were carefully selected according to specific criteria, and each demonstrated a significant reduction in pain following a test dose of intrathecal morphine. All patients had good pain relief from intrathecal morphine infusion, even with pain located in cervical dermatomes. Systemic narcotics could be withdrawn from most patients. Significant side effects were rare and typically self-limited. Many patients required gradually increasing doses, seemingly related to disease progression. Two patients with non-malignant pain have had variable dose requirements over 28 and 44 months without clear tolerance. In these patients we observed a reduction in side effects associated with systemic opioids when continuous intrathecal opioid infusion was instituted. Intrathecal opioid administration may have fewer complications than ablative pain relief procedures. In properly selected patients, this method offers an effective alternative for pain relief.