Supersymmetry (SUSY) offers the possibility of solving a number of theoretical problems of the Standard Model (SM). Thus the cancelations implied by the bose-fermi symmetry resolves the gauge hierarchy problem, allowing one to consider models at energies all the way up to the GUT or Planck scale. Further, using the SUSY SM particle spectrum with one pair of Higgs doublets. (pairs of Higgs doublets are needed on theoretical grounds to cancel anomalies and on phenomenological grounds to give rise to both u and d quark masses) the renormalization group equations (RGE) show that grand unification of the SM gauge coupling constants occurs at MG 21 10l6 GeV opening up the possibility of SUSY GUT models.