To compare the effectiveness and safety of controlled-release (CR) oxycodone tablets with immediate-release (IR) oxycodone in patients with chronic cancer pain, a multicenter, randomized, double-blind, parallel-group study was performed in 111 patients with cancer pain. Patients were treated with 6 to 12 tablets or capsules of fixed-combination opioid/nonopioid analgesics per day at study entry. Patients received 30 mg of CR oxycodone tablets every 12 hr or 15 mg of IR oxycodone four times daily for 5 days. No titration or supplemental analgesic medications were permitted. The mean (+/- SE) baseline pain intensity (0 = none, 1 = slight, 2 = moderate, 3 = severe) was 1.5 +/- 0.1 for the CR oxycodone-treated group and 1.3 +/- 0.1 for the group given IR oxycodone (P > 0.05). The 5-day mean pain intensity was 1.4 +/- 0.1 and 1.1 +/- 0.1 for the CR and IR groups, respectively (P > 0.05). Discontinuation rates were equivalent (33%). There was no significant difference between treatment groups in the incidence of adverse events. This study demonstrates that cancer pain patients given 6 to 12 tablets or capsules of fixed-dose combination analgesics can be equally well treated with CR oxycodone administered every 12 hr or IR oxycodone four times daily at the same total daily dose. CR oxycodone offers the benefits of twice daily dosing.