Background: Abdominal pain is one of the most frequent reasons for seeking care in an emergency department. Surveys have shown that patients are not satisfied with the pain management they receive. Reasons for giving inadequate pain management may include poor knowledge about pain assessment, myths concerning pain, lack of communication between the patient and healthcare professional, and organizational limitations., Objectives: The aim of the study was to investigate the outcome of nursing assessment, pain assessment and nurse-initiated intravenous opioid analgesic compared to standard procedure for patients seeking emergency care for abdominal pain. Outcome measures were: (a) pain intensity, (b) frequency of received analgesic, (c) time to analgesic, (d) transit time, and (e) patients' perceptions of the quality of care in pain management., Design: A quasi-experimental design with ABA phases was used., Setting: The study was conducted in an emergency department at a Swedish university hospital., Participants: Patients with abdominal pain seeking care in the emergency department were invited to participate. A total of 50, 100 and 50 patients, respectively, were included for the three phases of the study. The inclusion criteria were: ongoing abdominal pain not lasting for more than 2 days, ≥18 years of age and oriented to person, place and time. Exclusion criteria were: abdominal pain due to trauma, in need of immediate care and pain intensity scored as 9-10., Methods: The patients' perceptions of the quality of care in pain management in the emergency department were evaluated by means of a patient questionnaire carried out in the three study phases. The intervention phase included education, nursing assessment protocol and a range order for analgesic., Results: The nursing assessment and the nurse-initiated intravenous opioid analgesic resulted in significant improvement in frequency of receiving analgesic and a reduction in time to analgesic. Patients perceived lower pain intensity and improved quality of care in pain management., Conclusions: The intervention improved the pain management in the emergency department. A structured nursing assessment could also affect the patients' perceptions of the quality of care in pain management in the emergency department., (Copyright © 2010 Elsevier Ltd. All rights reserved.)