In 1968 he took up a position as Specialist Physician and Deputy Medical Superintendent of the Port Moresby hospital in Papua New Guinea.

In Papua New Guinea, he developed an interest in respiratory infections particularly the prevention of pneumonia, which led to work in the US on licensure of pneumococcal vaccine.

This interest led to a position with the World Health Organization, working on programs to reduce child deaths from pneumonia.

In 2001, after retiring as Emeritus Professor at The Australian National University, he founded Australia 21, a non-profit organization.

With the Nature and Society Forum, he helped to develop SEE-Change, an NGO in Canberra that works to enable Australians to connect with each other and the environment.