Abstract : For over one hundred years, the eigenvalue problem has been investigated by mathematicians, physicists, and engineers. Scientists explored the characterization, location, perturbation and computation of eigenvalues, to name a few topics. This thesis is devoted to the separation of eigenvalues. We will find the minimum gap between eigenvalues over an interesting class of tridiagonal matrices. We consider unreduced n x n symmetric tridiagonal matrices with all subdiagonal entries.