The first part of the dissertation addresses the co-ownership in current law. It outlines the historical development and illustrates the various application cases. The legal qualification of co-ownership is discussed critically, and a distinction is made from joint ownership. Furthermore, the applicability in the case of interest communities is examined. In the second part, the systematics and interpretative issues regarding the law of co-ownership are discussed. In addition to a multitude of detailed problems, the enforcement in co-ownership is presented. Finally, a critical review of the regulations on co-ownership is provided, along with a proposal for their amendment.