Vaso-occlusive crisis (VOC) is the primary cause of hospitalization of patients with sickle-cell disease. Treatment mainly consists of intravenous morphine, which has many dose-related side effects. Nonsteroidal antiinflammatory drugs have been proposed to provide pain relief and decrease the need for opioids. Nevertheless, only a few underpowered trials of nonsteroidal antiinflammatory drugs for sickle-cell VOC have been conducted, and conflicting results were reported. We conducted a phase 3, double-blind, randomized, placebo-controlled trial with ketoprofen (300 mg/day for 5 days), a nonselective cyclooxygenase inhibitor, for severe VOC in adults. A total of 66 VOC episodes were included. The primary efficacy outcome was VOC duration. The secondary end points were morphine consumption, pain relief, and treatment failure. Seven VOC episodes in each group were excluded from the analysis because of treatment failures. No significant between-group differences were observed for the primary outcome or the secondary end points. Thus, although ketoprofen was well-tolerated, it had no significant efficacy as treatment of VOC requiring hospitalization. These findings argue against its systematic use in this setting.