The Hydrologic Evaluation of Landfill Performance (HELP) program was developed to facilitate rapid, economical estimation of the amounts of surface runoff, subsurface drainage, and leachate that may be expected to result from the operation of a wide variety of possible landfill designs. The program models the effects of hydrologic processes including precipitation, surface storage, runoff, infiltration, percolation, evapotranspiration, soil moisture storage, and lateral drainage using a quasi-two-dimensional approach. In this document, some basic elements of the model are briefly described, input/output options are discussed in detail, and instructions for running the program on the National Computer Center IBM Computer System are given.