An experimental study of inelastic lateral torsional buckling of coped beams with simply supported ends is presented in this paper. Six full scale coped steel I-beam tests were conducted. The test parameters include the aspect ratio of cope length to beam depth at coped region as well as the ratio of cope depth to beam depth. The results of tests were compared with finite element model results. The test results showed that a reduction in the inelastic buckling load due to coping could reach more than 60% of the uncoped buckling capacity. A group of twelve finite element models for steel coped beams are investigated. The study takes into consideration variable parameters such as cope depth and length. A comparison between uncoped models and models with different geometrical parameters, is performed. The finite element results showed that both the cope length and cope depth have a significant influence on the lateral torsional buckling capacity. A parametric study of coped beams with stiffeners at coped region is reported in this paper. Based on the results of coped beams strengthened with either horizontal or vertical stiffeners, it is found that for cope depth to beam depth (d c /D) P 0.25; both horizontal and vertical stiffeners are required to prevent local web buckling at the coped region. ª 2014 Production and hosting by Elsevier B.V. on behalf of Housing and Building National Research Center.