Propofol has a high incidence of pain with injection, particularly into small veins. We sought to determine whether concomitant administration of lidocaine could prevent this pain. In a randomized double-blind trial, 368 women were allocated to one of four groups to receive 19 mL of propofol mixed with either 1 mL of 0.9% saline, 1 mL of 0.5% (5 mg) lidocaine, 1 mL of 1% (10 mg) lidocaine, or 1 mL of 2% (20 mg) lidocaine. The pain of injection was scored as none, mild, moderate, or severe. There was a significant reduction in the overall incidence of pain from 73% with saline to 32% with 20 mg lidocaine. A highly significant negative dose-response relationship between the dose of lidocaine and the severity of pain was demonstrable, both at induction of anesthesia and as recalled in the recovery room (P less than 0.001 for both). Lidocaine (20 mg IV) will significantly reduce the incidence and severity of pain with propofol injection, but about 6% of patients will still suffer unpleasant pain if the dorsum of the hand is used.