This series mainly consists of correspondence between Harold Edward Holt, as Prime Minister, and several foreign Heads of Government. Many of the eleven files include original signatures and associated diplomatic correspondence. 

The content of the files relates particularly to the Vietnam War, British withdrawal east of Suez and regional security in South East Asia. Other subjects covered include Rhodesia, British Guiana, food relief to India and Africa, official visits, Arthur Calwell's visit to Malta, the 50th Anniversary of the Russian Revolution of October 1917, the Greymouth mine disaster in New Zealand, and the July 1967 by-election for the seat of Corio (Vic).

The file numbering and titling system was imposed by the Prime Minister's Department. Each item includes the file number on a yellow label in the top right hand corner and a typed title label in the centre of the file cover. The top folio of each file is a summary of the contents. Many documents carry a security classification (up to Top Secret). The series was discontinued in December 1967, following Holt's disappearance, and transferred to archival custody in February 1989.