This document verifies that the undrained analysis of partially saturated soil is correctly implemented in PLAXIS. Bishop's effective stress (Bishop & Blight, 1963) is used in PLAXIS to handle unsaturated soil conditions. In undrained analysis, excess water pore pressures are generated based on the water bulk modulus, the value of which depends on the Soil Water Characteristic Curve (SWCC), i.e. the relationship between the degree of saturation and the applied suction. It is attempted to show how the SWCC affects the undrained behaviour of soil.