  In the first part of these lectures we will review the main aspects of large
N QCD and the explicit results obtained from it. Then, after a review of the
properties of N=4 super Yang-Mills, type IIB string theory and of AdS space, we
briefly discuss the Maldacena conjecture. Finally in the last part of these
lectures we will discuss the finite temperature case and we show how "hadronic"
quantities as the string tension, the mass gap and the topological
susceptibility can be computed in this approach.
