Inadequate Emergency Department (ED) pain management is well-documented. Optimal treatment of pain requires frequent pain assessment and opioid titration to effective dose due to large inter- individual variability in requirement. However titration is difficult to provide in this setting due to high patient to nurse and physicia ratios and multiple urgent competing patient demands. Patient controlled analgesia (PCA) has the potential to allow ED patients to actively participate in pain management by allowing self-titration to desired level of pain relief. An NINR funded randomized clinical trial (RCT) recently completed by our group provides promising preliminary support for the efficacy and safety of PCA for patients with abdominal pain at a single ED with a dedicated research nurse and standard loading dose given to all patients. Objective: To assess the ability of PCA to improve ED pain management Specific aims: 1) To compare the effectiveness and safety of PCA and non-PCA opioid analgesia when nurses involved in clinical care deliver the intervention to a broad group of ED patients with acute pain at multiple study sites. The primary hypothesis is that there will be a greater decline in pain over time and similar safety in patients randomized to receive PCA compared to patients receiving standard opioid analgesia. 2) To describe the feasibility of PCA in terms of patient and provider acceptance, resource utilization and cost associated with implementation and use. Innovation: PCA represents a novel shift from the current provider-driven model of ED pain management to one in which the patient is an active participant. Few prior studies have evaluated ED PCA and no systematic evaluation of time and resources exists. Methodology: An RCT will be performed at 3 clinical centers. 750 patients with acute pain warranting IV opioid administration will be randomized to receive usual opioid analgesia determined by the provider or PCA (loading dose 0.1 mg/kg morphine and demand dose of 1 mg morphine available every 6 minutes). Pain intensity will be measured by a numerical rating scale recorded every half hour up to 2 hours after initial opioid administration. Primary endpoints are rate of change in pain intensity from 30 minutes after initial administration of opioid to 2 hours as suggested by the results of the preliminary study and incidence of adverse events. PCA will also be compared to non-PCA opioid analgesia assessed at the end of the 2 hour study period by patient satisfaction with pain management; RN assessment of time efficiency/ease of use and satisfaction with pain management; and physician satisfaction with pain management. Resource utilization and cost associated with implementation and use of PCA in the ED setting will be assessed by total RN time spent on pain management per patient; pharmacy preparation time per patient; material cost per patient and RN and MD training time necessary for PCA implementation. Significance: If PCA is demonstrated to be effective, safe, and associated with patient and provider acceptance and acceptable resource utilization, it has the potential to significantly improve ED pain management.