Until recent years large incidental additions of sulphate in fertilizers, especially superphosphate and ammonium sulphate, ensured that the major sulphur requirements of crops were adequately met. Increasing purity and concentration of commercial fertilizers, however, have largely eliminated such additions, with corresponding increase in the importance of available soil sulphate and atmospheric sulphur. The latter can readily be measured but its contribution to crops is more difficult to assess. To examine one aspect of this question, the effect of sulphur in rain on the yield and sulphur content of oats has been measured by comparing pot cultures grown in two environments, one with access to both gaseous atmospheric sulphur and rain sulphur and the other to gaseous sulphur only.