Abstarct: The object of this thesis is to describe the theoretical aspect of hardening plasticity and to develop a finite element code to solve nonlinear problems. This dissertation is intended to be more practical and therefore focuses on the computer implementation of nonlinear finite element schemes. Nonlinearities arise in engineering situations from several sources. Nonlinear material response can result from elasto-plastic material behavior or from hyper-elastic effects of some form. Each of these nonlinearities may occur in a variety of structural types such as two- or three-dimensional solids, frxames, plates or shells. For this reason, elastic and the plastic relations thoroughly explained, furthermore the various yield criterions discussed in depth. Then the nonlinear solution methods are presented and finally a program for solving the elastic-plastic problems are developed. To verify the program, some conventional examples are analyzed and then the results are compared with a commercial finite element program.