4-Alkylamino-6-(C₃₋₅-hydrocarbyl)thieno[2,3-b ]thiopyran-2-sulfonamide-7,7-dioxides wherein the 4-alkylamino group is an ethylamino or propylamino are powerful carbonic anhydrase inhibitors useful in the treatment of ocular hypertension and glaucoma associated therewith.