4. ED attending physician's judgment that patient's pain warrants use of morphine: The factors that influence the decision to use parenteral opioids are complex and extensive. An approach that is commonly taken to address the issue of patient selection in drug trials is to use a specific condition (e.g., renal colic) or treatment (e.g., post-hysterectomy) that would generally be thought to be appropriately treated with an opioid analgesic, thereby eliminating individual judgment about eligibility for the study. However in order to assess the role of hydromorphone with the widest generalizability in the ED setting, we decided to enroll patients with a variety of diagnoses, all with a complaint of acute pain. Opioids are not an appropriate treatment for all patients who present with a complaint of pain (e.g., gastroenteritis, migraine). Therefore, unless there is a restriction to patients with a specific diagnosis, either a comprehensive list of diagnoses and situations in which opioids are indicated must be specified, or clinical judgment needs to be used. We have opted for the latter alternative.