Conditioning and disposal of solids has historically caused most of the operating difficulties and accounted for a significant portion of the capital and operating cost of wastewater treatment works. For that reason, a powerful incentive has always existed for the development of solids processing methods to improve operating efficiency and to lower costs. An additional incentive, only recently introduced, is the concept of “ultimate disposal” which has resulted in need for development of new methods for the treatment and disposal of sewage solids. This paper will first describe some of these methods and will conclude with a description of the solids processing systems of two major treatment works in Australia to illustrate this application of unit processes to meet specific objectives.