ABSTRACT The results of a comprehensive numerical study of the non-linear behavior of laterally loaded piles in stiff clay (characterized principally by the undrained shear profile) are presented. The analysis is carried out by means of a boundary element analysis of the soil (as a continuous body) coupled with the beam equations of pile flexure. The analysis accounts for the insitu lateral stresses and pile-soil adhesion. This is a new approach which departs radically from the traditional p-y method of analysis which assumes that the soil behaves as a set of nonlinear independent springs. The results of this study are presented in convenient dimensionless plots and equations, to facilitate application of the data to the design of piled foundations in the offshore environment. The design process is illustrated by example. Among the most important new results given in this paper are plots showing the lateral deflections, rotations and (maximum) bending moments of free am fixed-head piles as a function of load level. Also described are the effects of insitu lateral stresses and pile-soil adhesion. Non-linear effects are shown to be important under design loads. Excellent agreement was obtained by comparing the numerical results with published data from carefully conducted lateral load tests. This alternative to the traditional p-y method of analysis offers the designer an independent and convenient check (based on easily accessible soil data) of p-y computations. INTRODUCTION Lateral loading on piles results in soil yielding and opens up tension cracks in the soil near ground level even at moderate load levels. Lateral loading, therefore, cannot easily be analyzed by means of numerical models which assume linear behavior since there are significant practical differences in detail between the predictions of linear and non-linear analyses. Moreover, it is not clear how the choice of equivalent stiffness is to be made in such analyses. The well-known p-y method (1-3) does offer the practicing engineer a convenient means of analyzing pile behavior which recognizes the significance of the non-linear load-displacement response, albeit in a semi-empirical manner. The simplicity of this method, despite several theoretical and practical difficulties, has contributed considerably to its popularity. In this paper, we present an alternative approach based on current linearly elastic continuum analyses (4, 5) but which also incorporates the effects of constraints on the bearing pressures, tensile stresses and shear stresses which can be sustained by the soil. To avoid undue computational labor, an approximate solution of the problem has been derived which is similar in spirit to an algorithm described by Poulos (6). The advantages of this method of analysis is that it preserves the continuity of the soil mass (ignored in the p-y analysis), and perhaps, more importantly permits definition of the data and expression of the results in terms of meaningful soil parameters, namely, undrained shear strength.