1. Graded responses, in terms of both weight gain and food/gain ratios, were obtained to increasing increments of Na2SO4 added to diets containing suboptimal amounts of sulphur amino acids. 2. In most cases the relative efficiency of Na2SO4 ranged from 25% to 55% of that of synthetic methionine, when the former replaced 0-04 to 0-05 percentage units of the latter. This efficiency tended to be higher during the 3 to 5 than the 1 to 3 weeks of age periods. 3. The addition of either methionine or Na2SO4 decreased relative food consumption, which was apparently increased by suboptimal contentrations of dietary sulphur (as a compensatory response).