The influence of the inductive and mesomeric effects on the K X-ray production cross-sections (sigma(K alpha beta)) and average fluorescence yields ((omega) over bar (K alpha beta)) of sulphur atoms in aromatic thiophene ring was investigated. The samples were excited by 5.96 keV photons from a Fe-55 annular radioactive source. K X-rays emitted by samples were counted by an Ultra-LEGe detector with a resolution of 150 eV at 5.96 keV. It was observed the effects of the changing the number of CH2 groups bound to N-4 at position of 1,2,4-triazol-5-one on the K X-ray production cross-sections (sigma(K alpha beta))and average fluorescence yields ((omega) over bar (K alpha beta)) of sulphur in aromatic thiophene ring. (C) 2008 Elsevier B. V. All rights reserved.