The interface shear strength characteristics of soil-geomembrane are usually obtained by using large direct shear test device in a laboratory. The repeatability of these tests is very important as the design relies on the properties obtained from the test results. This paper investigates the variability of large direct shear test results by performing series of tests on smooth high-density polyethylene geomembrane samples. For the tests performed in this study, the test results show a scatter ranging from 5 to 65 percent depending on the parameter investigated. This magnitude of variability in the test results is significant and should be considered in the design. This paper presents the test results and a statistical analysis of repeatability of large shear tests used to obtain soil-geomembrane interface shear strength characteristics.