There are two main issues covered in the article: first, the concept of reciprocal synallagmatic) contracts and second, the legal structure (legal nature) of reciprocal obligations. It is widely recognized that the purpose of reciprocal or synallagmatic contracts is to exchange counter-performances between the parties. However, legal justification of synallagmatic contracts is controversial. According to the majority view the will of the parties expressed in the form of declaration of will is the source of reciprocal contracts (theories of subjective and functional equivalence). The author contests that notion arguing that reciprocal contracts - or at least vast majority of them, such as sale, work contracts etc. - are designed by law, and are not created by the will of the parties (theory of normative equivalence). Legal nature of reciprocal obligations has been subject of many debates since the 19 century. According to the majority view, a synallagmatic contract creates two obligations which are interdependent: each party is obliged to render its performance provided that the other party does the same (theory of interdependent obligations). The author argues that one should distinguish two levels of legal structure in reciprocal obligations. The first level consists of the parties' contractual obligations to provide their performances. The second level - which can also be described with the term synallagma - is intended to bind the parties' obligations in such a way so that they are to be exchanged for one another.