The purpose of our work was to determine, in a freshwater batch system, the importance and the direction of trace metal transfers between sediment and water as influenced by bacterial activity. Sediment was incubated in Meuse water in different conditions. Net transfer occurred on an average from sediment to water for Co, Cs, Cr, Cu, Hg, La, Ni, Zn and from water to sediment for Bi, Cd, Pb, Sb, Tl. Positive correlations between oxygen consumption and transfer of nine metals from sediment to water demonstrate the influence of bacterial activity. Correlations of the metal transfer either with water pH or with the variation of sediment weight at the end of incubation led to suppose that the alteration of the chemical conditions also strongly influenced the transfers. It was confirmed by the comparison of chemical characteristics of the water and of the sediment at the end of incubation in contrasted conditions. The uptake of 12 metals by a bacterial community isolated from the sediment was related to metal concentrations in the water. The specific transfer from the water to the bacterial biomass was appraised in the sediment incubation experiments. It allowed to compute the net metal transfer of 12 metals from the sediment to the water with significant bacterial activity. The comparison of these values with the transfers occurring at 4°C, i.e. with reduced bacterial activity, demonstrated that the transfer of 11 metals from the sediment to the water is clearly enhanced by bacterial activity.