Small-scale laboratory model test results on the ultimate uplift capacity of pipe piles in saturated clay are presented. Based on these and the limited test results conducted in the past, tentative equations for the variation in the adhesion/undrained-cohesion-of-the-clay constant with the undrained shear strength of clay have been developed. For a given undrained shear strength of clay, the net pullout load and the corresponding vertical deflection of piles can be expressed by a nondimensional equation. The nondimensional equation is independent of the embedment ratio of piles. (TRRL)