This diploma thesis deals with the legal historical development of political groups in the European Parliament from the formation of the ECSC in 1952 up to now. In the first chapter the term “parliamentary group” is defined and an explanation of the purpose of forming a political group is offered. The main part of this paper contains the development of political groups in the European Parliament over the last decades. Besides the genesis of parliamentary groups, also political and legal changes at European Community level and the constant further development of the European Parliament are taken into consideration. In the following chapter the elections to the European Parliament and the regulations concerning the seats in plenum are described, as these provide the basis for all the formations of political groups. The last part of this diploma thesis overviews the established law due to parliamentary groups and explains their respective organisation and working methods.