Diamond-like carbon (DLC) films are characterized by, among other properties, very low friction coefficients, high wear resistance, and high corrosion resistance. Depending upon the testing environment, the coefficient of friction can be as low as 0.01. As-deposited films are wear resistant in vacuum as well as in atmospheric ambient. This paper will discuss the general tribological behavior, in different environments, of DLC films deposited under a variety of conditions, and proposed mechanisms explaining the very low friction coefficients observed. The specific properties of DLC films deposited from acetylene by r.f. plasma-enhanced chemical vapor deposition will then be presented. The films were deposited at substrate temperatures between 100 °C and 250 °C, at various substrate biases. The films were annealed in vacuum at temperatures up to 590 °C. The tribological properties of the as-deposited as well as annealed DLC films will be presented as a function of the deposition parameters. The observed behavior will be discussed and related to other physical properties of the films. © 1991.