Land application systems are discussed with reference to the options available for applying wastewater and sludge to the site. Spray systems, surface flow methods, and sludge application schemes are all included with discussions of the advantages and disadvantages of each option within these categories. A distinction is made between the choice of treatment method and the application system. The selection of an application system is a function of the treatment alternative. Selection of alternative is made on the basis of fundamental soil, plant, waste and management factors pointing to overland flow, rapid infiltration, or irrigation as most appropriate for the given situation. Application systems described in this module include seven types of sprinkler irrigation techniques, gated pipe, three ditch systems, and the three most common field surface irrigation methods. Sludge spraying, spreading and subsurface injection are outlined. One important aspect of application system design is uniformity of wastewater contact with the treatment medium. This topic is addressed from a theoretical standpoint and related to the practical situation. A brief discussion of the special problems encountered in overland flow and rapid infiltration systems also is included. (Author/BB)