In the preparation of sulfated zirconia catalysts (SZ) by the controlled impregnation technique, the properties of the products, including catalytic activity, are influenced by the precursor from which Zr(OH)(4) is obtained, by the pH of its precipitation, and by the temperature and time of calcination after sulfation. The best catalyst for the isomerization of methylcyclopentane (MCP) to cyclohexane was obtained from zirconium oxynitrate as precursor, with precipitation of Zr(OH)(4) conducted at a constant pH of 7 and calcination in air, after sulfation as previously described, at 610 degrees C for 5 h. The nature of the chemical process occurring during calcination is discussed in the light of the results obtained.