In most engineering problems it is commonly practicaland convenient to use linear formulation. In studying theload-settlement behaviour of pile groups, homogeneous andlinear soil behaviour are usually used. However, if realisticresults are to be obtained, the nonlinear formulation shouldbe adopted especially in geotechnical problems.In this thesis, modeling soil nonlinearity is the maintask as the stress-strain relationship of soil is essentiallynonlinear. As soil nonhomogeneity is likely to prevail in mostsoil conditions, it is also accounted for in a consistentmanner.A group of piles connected with a rigid cap isconsidered to consist of two main parts. The rigid pile cap,imposing uniform displacements at the pile heads, isrepresented by plate bending finite elements. The second partis a group of piles embedded in the soil half space. Pile-soilinteraction is modeled by nonlinear load transfer curves andpile-soil-pile interaction is modeled using Mindlin’s equationfor point load within elastic half space.The factors affecting the load-settlement behaviour ofpile groups are presented and discussed herein. These factorsinclude, soil nonlinearity, soil nonhomogeneity, groupconfiguration, pile spacing, pile length and soil type. Thesefactors were found to greatly affect both the loaddistribution of different piles in the group and the groupsettlement.It could be concluded that, considering soil nonlinear-ityand nonhomogeneity generally rendered the pile groupstiffer behaviour than the case of linear homogeneousanalysis. The pile spacing seems to have great effect in theload-settlement behaviour of the pile group with less effectfor the pile length.