In this paper, a new elastic buckling interaction equation for simply supported rectangular plates is proposed, when the plate is subjected to five load components, such as compressions and bendings in two directions and shear. In order to construct this interaction, buckling strengths are calculated in addition to the existing data, and buckling interaction relationships for simply supported rectangular plates subjected to two load components are developed. The accuracy of these relationships is discussed. The accuracy of the newly proposed interaction equation is checked against the above mentioned interaction relationships for two load components. Further assessment of accuracy is carried out when a rectangular plate is subjected to more than two load components. It is found that the proposed equation yields results with accuracy sufficient for practical purposes. A comparison is also made with interaction equations proposed by Lloyd's Register and Det Norske Veritas. The result indicates that the new interaction equation proposed in this paper yields better accuracy in safety side.