A method to evaluate the capability to localize Gamma-Ray Burst (GRB) sources with the Gamma-Ray Burst Monitor (GRBM) onboard BeppoSAX is presented. The instrument is composed of four differently oriented detectors, so that their relative counting rates can be used to reconstruct the incoming direction of the GRB photons. The method involves the minimization of an energy- and direction-dependent&khgr;2-like variable related to the difference between the intensities observed by the four GRBM detectors and their expected values, as derived from the instrument’s response functions. The method is applied to a sample of GRBs simultaneously detected and localized by other experiments, in order to compare the achieved results with locations determined independently. ©2000 American Institute of Physics.