Treatment with opioid analgesics often causes adverse reactions that may make continuous use of such drugs difficult. We investigated the efficacy and safety of controlled-release oxycodone in the treatment of gynecologic cancer pain. The patients included 14 with cervical cancer, 6 with corpus cancer, and 17 with ovarian cancer. Treatment with controlled-release oxycodone was started at 5 mg/dose when pain control using nonsteroidal anti-inflammatory drugs became ineffective. The dose was titrated to the optimal level over a mean duration of 2.34 +/- 1.13 days, and the initially optimal dose was 18.92 +/- 5.23 mg/day. Although no patients experienced confusion, vomiting, or respiratory depression, 17 patients experienced adverse events, including constipation in 14 patients and nausea in 9 patients. The incidence of nausea was low in patients receiving oxycodone and prochlorperazine. In the present study, patients with moderate to severe pain caused by gynecologic cancer could successfully be treated with controlled-release oxycodone.