This paper deals with the development of simple lumped models of hydraulic transmission line. The models take into consideration the effect of viscous damping, fluidinertia, fluid compressibility and elas-ticity of line material. The developed models are one-directional;the fluid speed and pressure are thought of as averaged quantities over the cross section of the line. The simplicity of models result from the sepe-rate evaluation of the effect of the above mentioned parameters. The vali-dity of the models is discussed onthe bases of the comparison of the step and frequency responses of models with experimental results.