The Fe((SO4)(2)(NH4)(2))/TiO2 compound was prepared via the sol-gel technique at pH 9 dried at 70degreesC and treated thermally at different calcination temperatures (200, 400, 600 and 800degreesC). It was characterized by BET, XPS and XRD and it was tested as a catalyst for ethylene polymerization. A strong dependence was found between the structural properties of the support, the iron complex and the annealing temperature. Catalytic activity decreased with increasing heat treatment temperature up to 400degreesC and remained practically constant above this temperature. These differences occurred without important changes in the physical, chemical and structural properties of the synthesized polymer. (C) 2003 Elsevier B.V. All rights reserved.