In a double-blind, randomized, parallel-group study involving sixty patients with severe pain due to fractures, the analgesic activity of indoprofen and pentazocine was evaluated. Each patient received one of the following treatments in random order: indoprofen 400 mg i.v., pentazocine 30 mg i.v., placebo. The analgesic effect was measured by rating the intensity of pain before treatment and after 1/2, 1, 2, 4 and 6 hours. Patients' final opinions on efficacy were assessed on the basis of categoric and visual analogue scales. Highly significant differences were found between the active drugs and placebo for all variables analyzed. Indoprofen was significantly superior to pentazocine when assessed through variables measuring total analgesic effects. Since both drugs were well tolerated, i.v. indoprofen appears to offer an effective and safe alternative to narcotic analgesics in acute pain due to fractures.