The article deals with Rhetorical Structure Theory (RST). It is shown that the theory is a very helpful descriptive tool not only for microstructure but for macrostructure as well. The role of rhetorical relations in argumentative discourse in the sphere of science is described. The structure of Toulmin's argumentation model in the context of rhetorical relations is given. The relations taking place between the model components are analyzed. They are divided into four groups according to the type of causal link. All rhetorical relations are analyzed by means of decomposition into nucleus and satellite. The group of basic causal relations is parted in agreement with the degree of speaker participation. The group of Conditional relations is presented in full paradigm. In considering the group of purposeful relations such factors as cognitive states of readers and speakers are taken into account. Concessive relations are discussed from two points of view. Macrostructure of scientific papers argumentative discourse is outlined in the context of topical content. To describe macrostructure of discourse such multinuclear schemas as Joint are used. RST diagram for Introduction chapter is shown. The examples of all rhetorical relations taken from technical research papers are presented.