The reaction between roasted zinc blast-furnace dust (BFD) and ammonium sulfate was studied in the temperature range 250-450• C using different molar ratios to determine the maximum extraction of zinc. The reaction products are characterized. The composition of the untreated and roasted BFD, and reaction products was investigated by chemical, thermal, X-ray diffraction and fluorescence analyses. The decomposition of ammonium sulfate leads to the formation of (NH 4 )