The preparation method effect on the catalytic properties and hydrothermal stability of copper-loaded LTA (Cu-LTA) zeolites for the selective catalytic reduction of NOx with NH3 (NH3-SCR) has been investigated. Copper nitrate and liquid-state ion exchange (IE) was found to be the best for maximizing the SCR performance of Cu-LTA among the Cu sources and loading methods studied here. When fresh, the low-temperature (<= 400 degrees C) activity of Cu-LTA prepared in this way, denoted Cu-LTA(n)IE, is lower than that of the catalyst prepared using copper acetate via ion exchange. After hydrothermal aging at 900 degrees C for 24 h, however, Cu-LTA(n)IE shows a higher deNO(x) activity in the studied temperature range than any other catalysts. The overall characterization results show that the excellent hydrothermal durability of Cu-LTA(n)IE resulted from the stability of [2Z-Cu] species generated by locating Cu2+ ions onto Al pairs in the LTA framework.