Soil or dirt is defined as matter out of place. The common soils and their sources are listed. Soils are classified as air removable, wet cleanable, drysolvent cleanable, insoluble and unresponsive. The characteristics of each type are described and methods are given for treating each kind ofsoil or stain. Treatments with alkaline and acid solutions, with digesters and bleaches, with reduction and sequestrants, and with emulsifiers are discussed. Drying oil stains and non-drying oil stains and insoluble stains are considered. A practical pH guide for cleaning is given in table form. A table of 102 common soils or stains and how to remove them concludes the article.