The influence of calcination and reduction conditions, metal loading, impregnation solution pH, and dealumination treatment on the hydroisomerization of n-butane over bifunctional Pd/HZSM-5 catalysts was studied in order to obtain an active and highly selective catalyst. Temperature-programmed desorption of ammonia (TPDA), Fourier transform infrared (FTIR), atomic absorption spectroscopy (AA), chemisorption measurements, temperature-programmed reduction (TPR), and transmission electron microscopy (TEM) techniques were used to characterize the catalysts. Calcination and reduction conditions were found to have no significant influence on catalyst activity. When the catalyst was prepared by impregnation with palladium nitrate at pH 1.0 and then dealuminated with HCl, both conversion and isobutane selectivity were clearly enhanced. This is suggested to be due to palladium-proton adduct formation. The selected catalyst had a total conversion of 31.5 mol % and a high selectivity of 79%. Experimental conditions : weight of catalysts 5 g, reaction temperature 375 degrees C, total pressure 1 atm, W/Fn-C4 = 1 g/(g/h), and H-2/n-C-4 mole ratio 10:1.