Coster-Kronig processes are non-radiative transitions in which an inner-shell vacancy is transferred from one subshell of an atom to another. In this work, X-ray fluorescence cross-sections (sigma(Li), i = alpha, beta, & gamma, ) of the Tm element were measured at excitation energies of each L-i (i = 1, 2 and 3) subshells. Experimental measurements have been performed using an (24) Am annular source and a Si(Li) dedector. Absolute values of L X-ray cross-sections were calculated with incorporation of the enhancement due to the Coster-Kronig effect for Tm. The measured enhancement factors are smaller than the theoretically calculated values. (C) 2011 Elsevier B.V. All rights reserved.