The article explores little-studied dichotomous analysis. Dichotomous analysis is used in practice to solve many problems. However, to date there has been little research into the theory of dichotomous analysis as a special type of analysis. Dichotomous analysis includes three stages: decomposition of reality, composition of models and study of the resulting models. Decomposition is implemented using dichotomous division. Three types of dichotomous division are described, which produce three types of division results. Dichotomous analysis has different implementations. Dichotomous analysis is divided into: oppositional, aggregative, elemental. Elemental dichotomous analysis is performed using onomasiological division. Onomasiological division allows us to obtain information units or elements of the system under study. The article explores three types of dichotomous decomposition: decomposition to the selection of only parts or elements; decomposition to the selection of parts and constructive connections between them, decomposition to the selection of parts and causal connections between them. The content of the levels of dichotomous division is revealed. A formalization of the dichotomous composition is given. The relationships between the objects of decomposition in dichotomous analysis are described. A structural diagram of dichotomous decomposition is presented. Dichotomous decomposition does not apply to all objects, but only to those that have the property of separation. The dichotomy can be interpreted as a property and as a method. To describe multi-level decomposition, we use the apparatus of tensor algebra. In dichotomous decomposition and composition, paradigmatic and syntagmatic relations are used. The article describes the mechanism for searching for connections in dichotomous decomposition. The Bradford Hill model was used for this purpose. This model is transferred from the field of medicine to the field of information field.