A series of double-blind randomized trials was carried out in patients suffering from moderate to severe pain after meniscectomy to assess the analgesic effectiveness of diflunisal. In a single-dose study, 150 patients received either diflunisal (125 mg, 250 mg or 500 mg), aspirin (600 mg), or placebo, and hourly assessments were made of pain severity over an 8-hour period. The results showed that 500 mg diflunisal produced comparable relief to aspirin within 3 to 4 hours, but the analgesic effect continued for longer and was still very marked after 8 hours. A multi-dose study in 120 patients receiving doses of diflunisal (375 mg or 500 mg) or placebo confirmed the overall effectiveness of twice daily treatment with diflunisal. In a comparative study against oxyphenbutazone (200 mg t.i.d.), hourly pain scores made on the first post-operative day showed that a single dose of 500 mg diflunisal produced comparable relief over a 12-hour period to that with 2 doses of 200 mg oxyphenbutazone. Overall response to multiple doses was assessed as excellent or good by all the patients receiving diflunisal. Preliminary results are reported on the use of diflunisal in other painful conditions.