The as-synthesized alkali-free [Ga,Al]-ZSM-5 zeolites were steamed at different steam pressures (68 kPa less than or equal to P less than or equal to 92 kPa), reaction times (0 h less than or equal to t less than or equal to 9 h) and temperatures (530 degrees C less than or equal to T less than or equal to 800 degrees C). The obtained solids were characterized by XRD, FT-IR, N-2 adsorption, Al-27 and Ga-71 MAS-NMR. Acidity of the solids was characterized using n-heptane cracking (T=350 degrees C, P-N2/ P-C7=4, P=100 kPa) as a model reaction. Acidic or bifunctional behavior of these catalysts was determined using propane aromatization (530 degrees C, P-C3=100 kPa) as a model reaction. Steaming of solids, even at low temperatures (530 degrees C), leads to a profound and progressive demetalliation (degalliation and/or dealumination). Catalysts obtained under mild steaming conditions show for propane aromatization, properties similar to those of catalysts prepared by means of direct calcination under dry air at higher temperatures (T>700 degrees C), or by conventional impregnation methods. Solids steamed under more severe conditions (T greater than or equal to 600 degrees C or t>6h) present a strong dealumination and total degalliation, which leads to a strongly dehydrogenating catalyst, unable for aromatization, due to a drastic decrease of the number of acidic sites present on the zeolite structure.