The friction and wear behavior of chemical vapor deposition grown diamond films has been investigated under strong ultrasound conditions at the friction interface. Experiments were performed on an alternating "pin-on-plate" tribometer constructed as an ultrasonic motor with excited bimodal mechanical vibrations at the frequency of 20 kHz. Ultrasound sliding of the films was done against alumina ceramics and with the diamond film itself. We have shown that chemical vapor deposition diamond films can be fast polished mechanically without significant graphitization by ultrasonic treatment. The initial film roughness was reduced from an average R(a) approximate to 3000 nm to R(a) approximate to 10 nm. The polishing decreased the static coefficient of friction of the diamond film from about 0.53 to about 0.12. The operative mechanism for the polishing in the case of initially rough diamond samples appears to be asperity fracture. For smooth diamond samples it is suggested that tribochemical oxidation is also a polishing mechanism.