This paper describes a method for routinely checking the accuracy of individual cerrobend compensators made for use with the Varian Clinicomp-100. The Reduction Ratios (for a given beam energy) are provided for select depth of compensation and field size. It is important to check each compensator before commencing treatment to identify possible operation error and ensure proper filling of the styrofoam with cerrobend. This verification process involves: (1) choosing several points at which the tissue deficit is known; (2) exposing a ready-pack film (Kodak XV-2) in a polystyrene phantom at a suitable depth, both with and without the compensator in place (the dose to which the film is exposed is within the initial linear range of the H and D curve); (3) determining the optical density at the above chosen points; and (4) comparing the O.D. ratios corresponding to the compensated and uncompensated conditions to the Tissue Maximum Ratios (TMRs) for the proper depths at these points. The method of this technique is also incorporated into the quality control check of other compensators, for example, acrylic, brass c-wedges, etc.