[citation needed] In 1984, Sillence became the Foundation Head of the Department of Clinical Genetics at the Royal Alexandra Hospital.
He has been a member of many committees within the School of Public Health and Tropical Medicine, and the University of Sydney.
[citation needed] Sillence was instrumental in establishing the first working party to write guidelines for training in Clinical Genetics in Australia and was granted Clinical Geneticist status (1987) through the grandfather clause.
This certification model has been used by other Special Interest Groups within the Human Genetics Society of Australasia.
In 2012, Sillence delivered the Human Genetics Society of Australasia Oration, a prestigious lecture in his field.