This paper is a study on the so-called bilateral claims (actio duplex) of the Roman civil procedure in the context of their interpretation by scientists of the second half of the 19th — early 20th century. The author has scrutinized the monograph of E. Eck devoted to bilateral lawsuits. The monographs provides detailed conclusions of the scientist, who believed that as such the model of bilateral lawsuits was not typical for either the Roman or the civil procedure of his time. The paper also analyzes the current state of affairs in the theory of civil procedure in relation to these claims, and substantiates the law enforcement needs for the formation of a special approach to such phenomena. In the first part of the paper, we are talking about how ideas about bilateral claims of the Roman civil procedure developed mainly in German science by the beginning of the 20th century. In the second part of the article, the author concentrates on Eck’s monograph on the so-called bilateral lawsuits and sets out his views based on the study of Roman primary sources and their subsequent analysis. Eck’s arguments are also described in detail. This is about the non-dual nature of claims for the division of common property. The third part of the article focuses on modern Swiss civil procedure and Russian procedural realities. As a result, the author formulates a number of signs of claims related to the so-called bilateral award, which allow them to be considered as a separate legal phenomenon.