Surface acidity and propane transformation on In- and Ga-containing ZSM-5 type zeolites were investigated to find relation between the acidic character of catalysts prepared by conventional or solid state ion-exchange and the catalytic activity in alkane aromatization. On the basis of the concentration of Bronsted and Lewis acid sites measured by IR spectroscopy the In and Ga containing samples may be ordered into three main groups. The presence of Bronsted acid sites results in cracking of the hydrocarbon molecules, whereas the aromatization activity is attributed to Lewis acidity associated with the intimate contact of the oxide/zeolite assemblies.