Acute swelling of the hand is a common problem after trauma or surgery and is associated with both pain and loss of function. We describe a prospective study of 47 patients in which we assessed the effects of a pneumatic compression device (A-V impulse hand pump) on the swollen hand. The pump reduced swelling by increasing the velocity of venous return as demonstrated by Duplex scanning of the median cubital vein. Continuous use of the pump for 48 hours gave a reduction of 78.6% in swelling of the injured hand compared with the opposite, uninjured side. Even when used intermittently, with the pump on for 12 hours out of 24, a statistically significant effect was seen. There was a subjective reduction in pain and an objective improvement in function of the hand. Use of the pump resulted in a nearly normal hand by the time of discharge from hospital after, on average, 48 hours