The effectiveness of lysine acetyl salicylate (LAS) 1.8 g, equivalent to aspirin 1 g, in relieving severe, immediate, postoperative pain has been compared with that of morphine 10mg in comparable groups of patients. A single injection of LAS 1.8g did not give effective or consistent relief of pain, while morphine was both effective and consistent in its action. However, LAS was shown to have some analgesic activity.