The effectiveness of landfill-liner designs is evaluated in terms of the slope, drainage length, and saturated hydraulic conductivity of the lateral drainage layer, the saturated hydraulic conductivity of the soil liner, and the fraction of the area under a synthetic liner where leakage is occurring. The evaluation is performed using Version 1 of the Hydrologic Evaluation of Landfill Performance (HELP) model. The effectiveness is quantified by comparing the lateral drainage rate to the vertical percolation rate expressed as percentages of the total inflow. The two multiple-liner systems specified in the Hazardous and Solid Waste Amendments (HSWA) minimum technology guidance are shown to have different leakage-detection characteristics. One system detects significant leakage before leakage percolates out of the landfill, whereas the other system detects leakage only after significant leakage percolates out of the landfill. Four other designs were also examined-two with single liners and two with double liners. The two HSWA designs detected leakage at lower synthetic-liner-leakage fractions, but all designs with composite liners were nearly equally effective in reducing leakage from landfills. (Copyright (c) 1990, ASCE.)