Tests of sliding friction between identical polymer films have been carried out at sliding speeds of 0.0001 to over 10 m/s. In order to make measurements over such a wide range of speeds, three devices are employed. In each apparatus, a moving member with two identical polymer surfaces slides between two stationary blocks covered with the same polymer. The slow-moving crossarm of a standard Instron tester provides speeds of 0.0085 to 0.21 cm/s. A horizontal sled apparatus provides speeds of 1 to 10 cm/s. Finally, a modified impact test machine uses a pendulum that moves at about 3 m/s. Results with four polymer films illustrate a variety of behavior. The coefficient of friction, mu, for cellulose acetate decreases with increasing speed. Films of low-density polyethylene and polytetrafluoroethylene show increases in mu with speed. A film of ultrahigh molecular weight polyethylene shows only a slight decrease in mu with speed.