L 3 X-ray production cross sections have been measured for the elements in the atomic range 57⩽ Z⩽68 at 59.5 keV. The values of L 3 subshell fluorescence yields ( ω 3) have been measured for the same elements using the presently measured cross section values and the theoretical L i subshell photoionisation cross sections, Coster–Kronig transition probabilities, emission rates and vacancy transfer probabilities. The measured X-ray production cross section values are in general agreement with the theoretical values evaluated using L 3 subshell fluorescence yields, Coster–Kronig transition probabilities, emission rates, vacancy transfer probabilities and subshell photoionisation cross sections. Furthermore, the values of L 3 subshell fluorescence yields are in good agreement with the theoretical values.