The effects of temperature on the urease activity in soils in the presence and absence of toluene, a bacteriostatic agent, were investigated. The activation energies of the soil urease in the presence of toluene were much higher than those in the absence of toluene; however, the free energies of activation were essentially similar in both cases. From the considerations of enthalpies and entropies of activation of the soil urease and the previous observations regarding the association of soil urease in these soils, it is suggested that the urease activity in the presence of toluene is due to the extracellular enzymes adsorbed on or complexed with soil colloids.