A double-blind, placebo-controlled parallel-group study was carried out in 100 patients with postoperative pain. The analgesic activity of indoprofen given in a single dose as an i.v. bolus followed by a 2-h infusion, at total doses of 100, 200, and 400 mg was investigated. The highest dose of 400 mg was given additionally as an i.v. bolus alone. Intensity of pain was assessed before, and 30 min, 1, 2, 4, 6 and 8 h after treatment on a 0-4 point scale. An overall assessment was made at the end of treatment by the investigator and the patient using a 0-4 point scale and a visual analogue scale. Statistical analyses according to a multiple regression model on rating scale scores at fixed times and on overall assessments showed: (i) indoprofen was always more active than placebo in providing pain relief; (ii) there was a significant dose--response relationship; and (iii) there was no difference between the two schedules of administration of the largest dose.