Targets of LiCl (natural Cl) were irradiated with bremsstrahlung beams in the energy range 0.3-1 GeV and the mean cross-sections per photon were deduced for the prodn. of 27Mg and 28Mg from 35,37Cl. Comptete agreement was found between the experimentally determined yields and those calculaied by using a modified CDMD Rudstam formula