The available records show that the public relations of Zagrebački električni tramvaj (ZET) (English: Zagreb Electric Tram), a public transport authority in Zagreb, have existed even before the authority was legally established. This review covers the development of the communication practice of Zagrebački električni tramvaj (ZET), a required social factor, with the internal and external public. Previous public relations trends have been included, as well as the use of communication tools and methods, application of new technologies regarding relations with target groups and the communication reform concerning the implementation of innovative solutions. The paper uses a descriptive method to follow the public relations development by analysing available records from the legal entity's internal archives, publications and relevant scientific literature. Since the organisation concerned paid little attention to public relations, especially external, in its business activities from the very beginning to the present day, and it was mostly a closed unit in terms of formal communication, the conclusions on the development of communication practice are based on the interpretation of available sources and archives - the interpretation of photographs, questioning and other forms of direct information gathering.