Abstract The L-shell X-ray relative intensities I(Ll/Lα), I(Lβ/Lα) and I(Lγ/Lα) for Ba, Pr, Pt, Hg, and Bi, have been measured at the excitation energy of 20.48keV. Measurements have been performed using a system that consists of X-ray tube as an excitation source and Si(Li) detector. Theoretical values of the relative intensities have been calculated using theoretical values of L-subshell ionization cross-sections, L-subshell fluorescence yields, Coster–Kronig probabilities and fractional X-ray emissions. Experimental results have been compared with the theoretically calculated values. The measured values showed reasonable agreement with theoretical values.