Hydroisomerization of meta-xylene was carried out using catalysts containing 0.15-0.60 wt% Pt on H-ZSM-5 zeolite, in a pulsed microreactor system connected to a gas chromatograph at a flow of hydrogen of 20 cm(3) min(-1) and temperatures of 275-500 degrees C. Increasing temperature, increased isomerization with low rates. Increasing Pt content of the catalyst, decreased hydrodealkylation considerably via masking strong acid sites as revealed by temperature programmed desorption of ammonia measurements. Formation of trimethylbenzenes was inhibited by Pt incorporation in the H-ZSM-5 zeolite. The activation energies obtained for meta-xylene hydroisomerization were relatively low (24.4-61.6 kJ mol(-1)) on all catalysts under study. Para-xylene yields in the xylenes mixture of product relative to the corresponding thermodynamic equilibrium values amount to about 0.8-0.9 at temperatures of 400-500 degrees C but were lower at lower temperatures.