A simple test, based on the development of turbidity of grain extracts upon their dilution into a carbonate buffer, allowed the rapid identification of sulfur deficiency in wheat samples. Highly significant correlations between flour sulfur content and turbidity were found for sets of bread, cookie and multipurpose wheats, field-grown under a variety of sulfur and nitrogen fertilizer treatments. Turbidity was also highly correlated with sulfur contents of silo receival samples, which consist of any of a large number of cultivars. The method is equally applicable to wholemeal or flour samples, and turbidity development appears due to precipitation of certain sulfur-rich gliadin proteins. The rapidity of the test (as little as 30 min) and its simplicity and objectivity may allow its routine use for segregation of grain deficient in sulfur.