Comparisons of relative infiltration of summer thundershowers into undisturbed and treated western dry lands are necessary for guidance of future treatment practices. A system designed for measuring infiltration of simulated rainfall into small plots of undisturbed soil that can be hand-carried to sites inaccessible to vehicles has been developed. Disturbance of surface soil by driven plot frames or cylinders, a primary source of errors in infiltration measurement., has been eliminated in this design. Water requirements have been reduced to 1 or 2 gallons per measurement; so, distilled water or controlled chemical solutions can be used. Accurate measurements can be made rapidly and economically.