In this paper, we propose a new framework for opportunistic scheduling in wireless systems. We consider a TDMA type of multiple access scheme, in which only one user can be scheduled in each time-slot. For opportunistic scheduling for such a system, a nice framework has been developed in [1, 2]. However, in this paper, we consider a more general system that has a probabilistic scheduling policy and more general fairness constraints. Moreover, in addition to this generalization, we develop a new framework for opportunistic scheduling based on the duality theory. The duality theory is a well-defined theory in the mathematical optimization area. Hence, by using the framework developed in this paper, we can analyze the developed algorithm more rigorously and systematically.