Energy dispersive X-ray fluorescence spectroscopy is the preferred method for sulfur determination in fuels. However, it has not been evaluated below 100 ppm S (w/w), In order to assess its potential for the analysis of low sulfur diesel oils, an evaluation of reproducibility and repeatability was performed and the influence of C/H ratio was evaluated. Although matrix effects originating from variation in the C/H ratio of the sample are compensated in modem instruments, this compensation may produce some systematic deviation of measured concentration.