Intratumor infusion has been used to deliver therapeutic agents to tumor cells. The distribution volume of infused agents depends on the hydraulic conductivity (K) in tumors, which may vary with the infusion pressure. Therefore, we quantified K in a rat fibrosarcoma at different pressures, using an ex vivo perfusion technique. We found that both perfusion rate and K depended significantly on the perfusion pressure, and the pressure-induced changes in K could not be recovered completely within 12 hrs after perfusion. The change in K was presumably due to tissue compression. In addition, the perfusion rate and K depended on tissue temperature. The temperature dependence was mainly caused by the viscosity change in the perfusate. These data suggest that effects of perfusion pressure on K can not be neglected in optimization of intratumor infusion of therapeutic agents.