Sulfur and selenium isotopes are used for labeled compounds and as precursors for radioisotope production; however, both limited availability and high costs are problems. A new method is needed for large-scale separation of these isotopes. Experimental distillation columns were used to measure isotopic separations for sulfur and selenium compounds. The maximum total isotope separation of 32S vs. 34S were 1.127 for H2S, 1.048 for COS, 0.838 for SF4, and 1.058 for CH3SH. Relative volatilities of 32S vs. 34S are 1.0006 for COS and 0.9976 for SF4. There is a reverse isotope effect for carbon in COS. No isotopic separation was observed for dimethyl selenide. The lower mass selenium isotopes in H2Se are more volatile. Distillation is a promising method for separating sulfur isotopes on a production scale. Existing distillation technology produced separated isotopes with an effect similar to that found for sulfur in SF4. 8 refs., 2 tabs.