[1] He served three terms as Director-General of the World Health Organization (WHO) from 1973 to 1988, and is widely known for his effort to combat tuberculosis and his role in having shaped the landmark Alma Ata Declaration that defined the Health for All by the Year 2000 strategy.

[6] In 1951, Mahler joined the World Health Organization (WHO) and spent almost ten years in India as Senior WHO Officer attached to the National Tuberculosis Programme.

From 1962, he was Chief of the Tuberculosis Unit at the WHO Headquarters in Geneva until 1969, when he was appointed Director, Project Systems Analysis.

In the same year, the Executive Board of WHO issued the report "Organizational Study on Methods of Promoting the Development of Basic Health Services".

Mahler was left to champion a more holistic and inclusive approach to health care on his own and with his departure as the Director-General, the WHO lost its political profile.