Biological treatment of metal-containing wastewaters with sulphate-reducing bacteria (SRB) is an attractive technique for the bioremediation of this kind of medium. In order to design a suitable engineering process to address this environmental problem, it is crucial to understand the inhibitory effect of dissolved heavy metals on these bacteria. Batch studies were carried out to evaluate the toxic effects of several heavy metal ions [Cr(III), Cu(II), Mn(II), Ni(II) and Zn(II)] on two cultures of SRB (Desulfovibrio vulgaris and Desulfovibrio sp.). The experimental data indicate that SRB show different responses to each metal. At the highest metal concentration tolerated for each metal, the precipitation levels for D. vulgaris were as follows: 24.7%-15 ppm Cr(III), 45%-4 ppm Cu(H), 60%-10 ppm Mn(II), 96%-8.5 ppm Ni(H) and 9%-20 ppm Zn(H). The corresponding values for Desulfovibrio sp. were: 25.5%-15 ppm Cr(III), 71%-4 ppm Cu(II), 66.2%-10 ppm Mn(H), 96.1%-8.5 ppm Ni(II) and 93%-20 ppm Zn(H). Results obtained in batch studies will be taken into account for the subsequent design of a sulphate-reducing bioreactor to reduce levels of heavy metals present in different types of contaminated media. (c) 2005 Elsevier B.V. All rights reserved.