The second volume of the official history of the Department of External Affairs, Coming of Age covers a period of remarkable expansion and achievement in Canadian external relations.

In 1946, with its own minister for the first time, the Department of External Affairs embarked on a period of impressive growth and assumed responsibility for a broader range of foreign policy issues than ever before. Under the expert guidance of Lester Pearson, for a decade the department enjoyed popular and parliamentary consensus about international interests. The election of the Diefenbaker government in 1957 deprived the department of Pearson's experienced ministerial direction and exposed it to new priorities and new ways of doing things. At this time foreign policy consensus began to erode. As well, there was pressure to respond to the administrative revolution inaugurated by the Royal Commission on Government Organization (the Glassco Commission) appointed in 1960. After Pearson returned to office as prime minister in 1963, questioning by the public, and also by the governing party and the cabinet, became more fervent.

Coming of Age concludes in 1968 as indications of a challenge to the principles underlying Canadian foreign policy emerged from a new generation of ministers, a challenge that would produce major changes after Pierre Trudeau became prime minister.