An evaluation of the analgesic effects of preoperatively administered ibuprofen on prospective pain after the surgical removal of impacted third molar was undertaken in 100 patients in a double-blind parallel treatment trial. The pretreatment with ibuprofen delayed the mean time of onset of postoperative pain more than 100 minutes, as compared to pretreatment with placebo. The severity of pain initially experienced postoperatively was less in the pretreated group. There was no detectable interaction between the pretreatment and the analgesics administered postoperatively. The results of this study suggest that it is possible to delay the onset and lessen the severity of postoperative pain by preoperative administration of a nonsteroidal, antiinflammatory analgesic, such as ibuprofen.