About 1930 Dr. Stephen Szego of Hungary developed the diagrid structure. During the early years diagrid structures were of reinforced concrete. In recent years the structural continuity can be achieved by welded steel beams. The purpose of this thesis is an investigation of a plane diagrid having two sets of grid beams dividing the four 20' edge beams into three equal spaces. These two sets of grid beams are perpendicular to each other. The manner of loading of the panels is uniformly distributed. By reducing some simple equations sixteen simultaneous equations have been obtained instead of twenty-six. By writing the sixteen simultaneous equations into matrix form and then transforming it into computer language, by using two subprograms, solutions are obtained. A study is made to show the effect of moments, deflections, reactions, rot. ations by changing the column size and the ratio of I_EB/I_G. / Master of Science