This year’s 90th anniversary of the establishment of Interpol, known between 1923 and 1956 as the International Criminal Police Commission, provides a good opportunity to present the transformation of its membership throughout the whole period. It is a history of slow, yet consistent establishing of the state element in this international organization. This ultimately ledto its transformation and acquisition of an intergovernmental nature, which is considered to be very rare in the circle of international organizations. At the early stage the implementation of the plan of the Commission’s establishment was accompanied by a strange and unclear idea of a membership of a mixed, private-public nature. It was not until the following years, particularly 1932, whenthe principle of state participation corresponding to real and practical needs of the international cooperation in the sphere of combating crime was emphasized more clearly and strongly. Despite ambiguous statutory formulations, starting with the Brussels conference in 1946, this trend has become permanent in the internal order of this international organization. The case study was based on international documents of the Commission, the circumstances surrounding its establishment and later activity, and Polish documents preserved in the archives of the state.