Non-steroidal anti-inflammatory drugs are theoretically contra-indicated in the haemophilias but might be useful for those patients with chronic arthritic pain, as long-term strong analgesics are also undesirable. We carried out studies of platelet function and coagulation in 8 normal controls and 7 haemophiliacs while they were taking sequentially benoxaprofen and salsalate. No significant alterations in platelet function, bleeding time or coagulation occurred with either drug. In a subsequent double-blind controlled clinical trial using ibuprofen and placebo 8 of 9 patients had a significant reduction in pain score whilst using ibuprofen without significant change in the frequency of bleeds or the amount of concentrate used. Laboratory measures of coagulation also failed to reveal any adverse effect of the active drug. Non-steroidal anti-inflammatory drugs may be beneficial and may be used with caution in haemophilia.