In seven defined samples of grass and in six samples of maize silage the contents of sulphur and chlorine were determined by two analytical procedures: both elements with X-ray fluorescence spectrometry (XRF), sulphur separately with inductively coupled plasma – atomic emission spectrometry (ICP-AES) and chlorine according to Volhard (Skoog and West, 1963; Official Journal of the EC, No.L. 155/13, 12/07/71). The average contents of sulphur in grass silage, g kg–1 DM, were 2.53 g and 1.91 g, in maize 0.87 g and 0.75 g by XRF and ICP-AES, respectively. The differences in the content of sulphur between the two methods were statistically significant (P < 0.01 and P < 0.05). The average contents of chlorine in grass silage, g kg–1 DM, were 7.69 g and 9.09 g, and in maize 2.00 g and 2.55 g by XRF and Volhard, respectively. The differences between the two methods were statistically significant (P < 0.01).