Total M shell X-ray production cross section for 11 elements with 69 less than or equal to Z less than or equal to 92 have been measured using an incident photon energy of 5.96 keV. Measurements have been performed using an Fe-55 annular source and a Si(Li) detector. Average M shell fluorescence yield at each incident photon energy has been deduced, using the experimental total M X-ray production cross section and theoretical M shell photoionization cross section. Present experimental results are compared with other experimental and theoretical values. Reasonable agreement (to within 0.3-28%) is typically obtained between present and other experimental and theoretical values. (C) 2004 Elsevier Ltd. All rights reserved.