Between 1940 and 1970 the New Zealand Government undertook an extensive expansion programme of hydro-electric power infrastructure across New Zealand’s North and South Islands. This paper documents the advice and collaboration that occurred between the New Zealand Government and various agencies of the Governments of the United States of America and Australia Material is drawn from New Zealand and Australian archival sources covering newspaper articles, the proceedings and publications of professional societies, and official correspondence, publications and reports of New Zealand government departments. These sources are discussed chronologically across a range of professional jurisdictions.