We sought to determine Emergency Department (ED) patient preference for oral (p.o.), intramuscular (i.m.), or intravenous (i.v.) pain medication and patient expectations of time to medication effect by route. A prospective, observational study of 1276 patients presenting with painful illness or injury was performed in a university ED. Patient preferences were 66% p.o., 15% i.m., and 19% i.v. pain medication. Patients aged greater than 55 years were more likely to prefer parenteral medication than younger patients. Patients in severe pain were also more likely to prefer parenteral medication than those with less severe pain. Despite these differences, a majority of patients in all groups preferred oral medications. There were no differences in preference based on ethnicity or gender. Patient expectations for time to pain medication effect were 27 min p.o. (95% CI 26-28), 12 min i.m. (95% CI 11-13), and 7.5 min i.v. (95% CI 6.9-8.0).