The efficacy of ibuprofen as a pre-emptive analgesic for postoperative pain was investigated in 81 children in the age between one and four years subjected to elective surgery. The patients were randomized into two groups receiving rectally either ibuprofen 40 mg.kg-1.d-1, divided into four equal doses, or placebo in a double blind manner. Additional pain relief was provided by morphine. In the recovery room ibuprofen provided superior pain relief during the first hour and significantly reduced the need of morphine. Heart rate and arterial blood pressure were lower in children who received ibuprofen, probably reflecting better analgesia. The side effects were mild and similar in both groups. We conclude that rectal ibuprofen is a safe analgesic in children in the age between 1 and 4 years and reduces the need of opioids for postoperative pain relief.