Objective The purpose of this study was to investigate patients' perceptions of the effectiveness of a pain management regimen, which consisted of intermittent prn bolus doses of morphine, in a critical care unit after cardiac surgery. Design This was a escriptive and correlational study. Setting This study took place at the cardiothoracic intensive care unit of a major teaching hospital in Sydney, Australia. Patients The subjects were 102 patients who underwent cardiac surgical procedures. The mean age of the group was 61 years, and 24.5% were females and 75.5% were males. Results Analysis revealed that patients received limited total amounts of morphine during their critical care stay (mean = 26.7 mg; SD = 13.3; range: 0-68). All activities were associated with increased pain sensation. Patients requiring an internal mammary artery graft experienced increased pain despite receiving greater amounts of morphine. Elderly patients received less morphine and were refused pain killers more often than younger patients. Females found their overall pain experience to be less acceptable than did males. Less than half the participants always communicated their experience of pain to nurses. Conclusion Overall, the majority of participants were reasonably satisfied with their pain experience. However, the following areas need improvement: the assessment and management of pain in relation to gender and age differences and the type of graft/s used; the administration of morphine before activity; and the communication of pain experience by patients.