A well structured computer program has been developed to implement and compare two models for geometrically nonlinear finite element analysis of plane frames. One model is developed using classical beam-column theory, and the other is formulated using standard finite element techniques. The beam-column model is shown to converge to a more accurate equilibrium path using less elements to model a structure than the second model for frames. The models are also compared on the basis of their limitations and on the basis of the degree of difficulty for their implementation. The modified Riks/Wempner method is used to perform postbuckling analysis and to study the effect of varying the composition of the tangent stiffness matrix on its ability to detect instability. The importance of including all contributions in the incrementation of a model derived using convected coordinates is also studied. / M.S.