Relations of obligation marked by multiple individual elements are regulated in polish civil code. The most representative, except for mutual obligations, are joint and several obligations. The fact, that in the structure of joint and several obligations there are multiplication both in entity element and in contents is an evidence that right from the beginning joint and several obligation should be treated as one relation of obligation what excludes multiplicity of obligations. This kind of approach to the joint and several obligations seems to be right because of the interpretation of the art. 554 of the civil code excluding this regulation from the group of the sources of joint and several obligations by law.