In this thesis equiangular lines are discussed. They are interpreted in terms of algebraic graph theory. The absolute bound and the relative bound for maximum number of equiangular lines are proved. Switching, switching classes, switching graphs and two-graphs are defined. Rigorously, as well as through examples, the one-to-one correspondence between switching classes, switching graphs and two-graphs is demonstrated. Regular two-graphs and their significance in the analysis of equiangular lines are introduced. The basic properties of strongly regular graphs are proved. Through examples, Paley graphs are described as a class of strongly regular graphs. The relation between strongly regular graphs and regular two-graphs is depicted. Feasible parameters of strongly regular graphs and regular switching graphs are listed. The method of finding the optimal equiangular set using Paley graphs is described. Using Paley(17), an equiangular set in \(\R^9\) is constructed.