A series of laboratory model tests on the suction pile installation in sand have been conducted to obtain the relationship between the applied suction pressure inside the pile and the resulting pile penetration. The relationships have been used to estimate the mobilized soil strength during the pile installation. This reduction in the soil strength due to the applied suction pressure is described as a function of a nondimensional parameter to characterize the variation and transition of the soil strength during the pile installation. The nondimensional parameter includes all pertinent pile and soil properties that are thought to affect the behavior of the suction pile during installation.Key words: suction pile, suction pressure, mobilized effective soil friction angle.