The collection primarily contains items concerning Mr. Kostelecký's career with the United Nations, namely his activities with the United Nations Appeal for Children (UNAC) and his work with the United Nations Economic Commission for Europe (UNECE), including his work on as a consultant on the official history of UNECE: “Three Decades of the United Nations Economic Commission for Europe” (E/ECE/962).

There is also correspondence between Kostelecký and Myrdal about the ECE history project, including the preparatory work for Kostelecky's book “The United Nations Economic Commission for Europe: The Beginning of a History”. This material includes records of interviews with figures prominent in the UNECE, including Gunnar Myrdal, Walt Rostow, and Evgeny Chossudovsky, among others.

The collection also contains correspondence with the Kostelecký and Myrdal families and the Swedish Labour Movement Library and Archives about donations of Kostelecký and Myrdal's Papers, as well as Kostelecky’s publications and several books from his personal library.

There are numerous photos, four framed portaits, and several film negatives in the collection, including portraits of Kostelecky and other United Nations staff members, as well as more personal photos of the Kostelecky and Myrdal families. Primarily, however, there are photos relating to the work of the UNECE. In total, there are over 300 photographs in the collection.