The lateral torsional buckling of coped steel I-beams was investigated extensively by a number of researchers. Design recommendations have been proposed by Cheng and Yura. They proposed a set of interaction equations to evaluate the elastic lateral torsional buckling capacity of coped steel I-beams based on the interaction of the lateral torsional buckling capacity of the coped (tee-section) and the uncoped regions. However, these interaction equations may not be appropriate for sections with a small ratio of cope length to web depth of the tee-section because local web buckling of the tee-section may occur. In this paper, modified interaction equations based on an analytical study of tee-sections are proposed with improvement over Cheng and Yura's interaction equation. For symmetrical loading, the use of the equivalent moment coefficient C_b in Cheng and Yura's design interaction formula for calculating the critical moment of coped I-beams may produce non-conservative results. Subsequently, a modified interaction formula is proposed.