We have performed new determinations of sulphur and silicon abundances for a sample of 26 disk stars based on high-resolution , high signal-to-noise spectra .
The results indicate a solar [ S/Fe ] for \mbox { [ Fe / H ] } > -0.3 , below which [ S/Fe ] increases to \sim 0.25 dex at \mbox { [ Fe / H ] } = -1.0 .
We find that there is a good correlation between [ S/H ] and [ Si/H ] , indicating the same nucleosynthetic origin of the two elements .
It seems that the ratio of sulphur to silicon does not depend on metallicity for \mbox { [ Fe / H ] } > -1.0 .
The implications of these results on models for the nucleosynthesis of \alpha -capture elements and the chemical evolution of the Galaxy are discussed .