4.0$ imes$10-3 (IU/cells/day) of maximum specific scu-PA production, which was higher than those by a 75$ extrm{cm}^2$ T-flask and conventional perfusion systems, was maintained by tube-type bioreactor at 0.35 (1/h) of perfusion rate corresponding to 0.15 (dynes/$ extrm{cm}^2$) of shear stress. The production of scu-PA is also increased as shear stress was slowly increased, which is similar to natural human blood circulation. The tube reactor proves that there may be no limitation of oxygen supply by showing 1.0 (1/h) of oxygen transfer coefficient at steady state and this system yields much lower shear stress of 0.3(dynes/$ extrm{cm}^2$) than that of 5-8(dynes/$ extrm{cm}^2$) by conventional agitation systems.