The analog technique is applied to the analysis of flood runoff. A quasi-linear analog model has been developed for simulating the runoff-producing characteristics of a drainage system. Where storage is linear a unique relationship correlating the inflow and outflow peaks is derived. The technique for synthesizing flood-frequency distribution is also discussed. It is found that a linear-basin system would not modify the type of probability distribution of its inflow, whereas a nonlinear-basin system would.