L X-ray fluorescence cross-sections of some elements in the atomic number range 50 ≤ Z ≤ 59 have been calculated theoretically according to subshell excitation energies of elements. The Coster-Kronig transitions (f12, f23, and f13) are non-radiative transitions. The Coster-Kronig enhancement factors due to the effect of the CosterKronig transitions on L X-ray fluorescence cross-sections have been calculated theoretically. The calculated values have been compared with other earlier experimental and theoretical values.