The K shell fluorescence yield omega(K) of Cd and Zn in Cd1-xZnxS semiconductors has been studied. Energy dispersive X-ray fluorescence (EDXRF) technique was used to measure K X-ray photons. Cd and Zn elements were excited by using 59.5 keV photons emitted by a 50 mCi(241) Am radioactive source. The emitted characteristic K X-rays were detected by a Si (Li) detector having a resolution of 160 eV at 5.9 keV. It was found that the K shell fluorescence yield COK changed in Cd1-xZnxS thin films for different compositions of x. (c) 2006 Elsevier B.V. All rights reserved.