The theoretical basis and the experimental specifics are presented for a generally valid, systematic procedure which effectively achieves simultaneous balance of x-ray filter pairs over a wide range of wavelengths. K irkpatrick's technique of adding a third material to one of the filters is necessarily employed. Corollary topics discussed include the preparation of filters and holders, criteria for balance, methods of testing for balance, and the role of pulse-height analysis in the balanced-filter technique. It is shown how a number of points of possible experimental difficulty may be recognized and overcome. Results obtained by following the described procedure are presented.