This study was designed to evaluate whether the nurses' assessment of postoperative pain can be an alternative to patients' self-reporting. We examined 187 patients receiving postoperative intravenous patient-controlled analgesia. The nurses assessed the patients' pain with three pain indices (therapeutic efficacy, pain intensity, and facial pain expression) 8 hr after operation. The patients recorded their resting and movement pain using 100-mm visual analog scales immediately following the nurses' assessment. There was an acceptable correlation between overall pain measurement assessed by patients and that assessed by nurses (canonical correlation coefficient=0.72, p=0.0001). The resting pain was more reliably reflected than the movement pain in overall measurement assessed both by nurses and by patients. Among the three pain indices assessed by nurses, the pain intensity most reliably reflected the patients' self-reports. The pain intensity assessed with a simple verbal descriptor scale therefore is believed to be an effective alternative to the patients' self-reports of postoperative pain at rest. However, it mirrored the patients' self-reports during movement less reliably. Therapeutic efficacy and facial pain expression indices were not effective alternatives to patients' self-reporting.