The use of the Sterile Insect Technique to control and/or eradicate insect pest populations has been extensively applied to medfly. However, patented differences in sexual compatibility between populations or strains from different origins has been a serious concern to a wider use of sterile flies, and in particular sterile males of genetic sexing strains (GSS). In the present experiments, the sexual compatibility and mating performance of flies from 9 countries representing 5 continents and 4 GSS were measured. It is demonstrated that, from a qualitative standpoint, wild medfly populations world-wide have not yet evolved specific sexual behaviors indicative of incipient pre-mating isolation mechanisms under local natural selection. Wild medfly populations are as sexually compatible with GSS as they are with other wild populations. On that basis, the same mass reared strain can now be used worldwide, as long as it fulfills the standard quality control requirements.