Softly-broken N=4 supersymmetry in the large-N limit

We calculate the exact values of the holomorphic observables of N = 4 super symmetric SU(N) Yang-Mills theory deformed by mass terms which preserve N = 1 SUSY. These include the chiral condensates in each massive vacuum of the theory as well as the central charge which determines the tension of BPS s aturated domain walls interpolating between these vacua. Several unexpected features emerge in the large-N limit, including anomalous modular properti es under an SL(2, Z) duality group which acts on a complexification of the 't Hooft coupling lambda = g(2)N/4 pi. We discuss our results in the contex t of the AdS/CFT correspondence.