This book is divided in two parts. The first one which comprises chapter 1 and 2 regards the perturbative inspection of a highly non trivial super-conformal model. I present the explicit computation of a wide class of four point Green functions up to the second order in the gauge coupling. Then using the conformal Operator Product Expansion (OPE) I extract informations about the spectrum (conformal dimensions) and the trilinear couplings of the theory. The second part which comprises chapter 3 and 4 contains some topics concerning instanton computations in supersymmetric gauge theories. In...