Bioleaching rates are affected by temperature and temperature is a major selective pressure for the organisms that will inhabit a bioleaching operation. The relationship of microbial activity to temperature is best described by the Ratkowsky equation. Ratkowsky and Arrhenius equations were applied to temperature versus sulfur or ferrous iron oxidation data for selected bioleaching microorganisms. Extrapolated cardinal temperatures for iron and sulfur oxidation, and activation energies were derived from the fitted Ratkowsky and Arrhenius equations. The data provided definition of the temperature operating windows, to a precision not previously available, for the majority of species that are frequently encountered as the biological catalysts in tank and heap bioleaching environments. (c) 2005 Elsevier Ltd. All rights reserved.