Octafluorothiolane and octafluoro-1, 4-dithiane have been obtained directly and in up to 15% and 60% yields, respectively, from reactions of sulfur with tetrafluoroethylene. 2- Trifluoromethylpentafluoro-1, 3-dithiolane was usually obtained as a by-product. Similar reactions of tetrafluoroethylene with selenium and phosphorus in the presence of iodine gave octafluoroselenolane, octafluoro-1, 4-diselenane, octafluoro-1-iodophospholane, ...