This chapter presents an introduction to cross-layer scheduling and resource allocation for wireless systems and an overview of some of the approaches and proposed algorithms. The use of scheduling is motivated by first considering the fading Gaussian channel. Then, the focus shifts to scheduling and resource allocation for cellular systems. Existing approaches for the uplink and the downlink are discussed, as well as research results relating to the fading Multiple Access and the fading Broadcast Channel. Schemes for OFDMA and CDMA systems as well as systems using multiple antenna transmission are also presented. It is hoped that this survey will affirm the improvement in performance that can be achieved by use of cross-layer approaches in the design of Next-Generation Networks.