Zr(OH)(4) samples were prepared from ZrOCl2 and ZrCl4; they were calcined at temperatures between 100 and 620 degrees C and were sulfated with H2SO4 solutions. The catalytic activity in n-butane isomerization of these samples (at 300 degrees C, 1 atm, and WHSV = 2.5 h(-1)), previously activated in air at 620 degrees C is not well correlated with their textural properties or the SO42- concentration. Zr(OH)4 samples calcined at temperatures higher than 375 degrees C are crystalline and adsorb SO42- groups, but which are not active catalytically. The catalytic activity decreases with the calcination temperature in a similar way as the OH groups (determined by chlorination) are eliminated, forming less reactive surface groups. When the crystalline samples are sulfated with H2SO4 vapors, catalytically active materials are produced, irrespective of the crystalline state. The drastic sulfation overcomes the inertness of the crystalline surface and catalytic active sites for n-butane isomerization are produced. This in situ resulfation may also compensate the sulfur losses during the reaction.