Sulfur isotopic analysis of the elemental sulfur reference material Soufre de Lacq, prepared as silver sulfide by chromous chloride reduction and as copper sulfide by sealed-tube synthesis, indicates that Soufre de Lacq is isotopically homogeneous across different size fractions to within analytical uncertainty (??0.15???). The sulfur isotopic composition of aliquots of Soufre de Lacq prepared by these two techniques are identical to within analytical uncertainty. The mean sulfur isotopic composition for Soufre de Lacq prepared as silver sulfide and copper sulfide (relative to VCDT) is +16.20 ?? 0.15??? (1??).