He is an adjunct professor in Sustainability and Co-Director of the Alliance 21 project at the United States Studies Centre at the University of Sydney.

[2] After the Liberals' defeat (their fourth consecutive loss) at the 1990 federal election, Hill became Leader of the Opposition in the Senate (1990–96), and held appointments during these years as Shadow Minister for Foreign Affairs, Defence, Public Administration and Education, Science and Training.

Following the landslide election victory of the Liberals under John Howard in 1996, Hill became Leader of the Government in the Senate (1996–2006) and Minister for the Environment (1996–98).

However, one of The Age's senior journalists, Michelle Grattan, said on 31 March 2008 "Hill had not really wanted to leave Parliament, but John Howard was anxious to get him out."

On 15 March 2006, Hill resigned from the Senate and, two days later, was appointed Permanent Representative to the United Nations for Australia, replacing Caroline Millar.

[7] The diplomatic appointment made upon his retirement from Parliament was arranged by Foreign Minister and former Liberal leader Alexander Downer.

It has been alleged that when Downer was Opposition Leader in 1994 he had failed to back Hill's bid to move to the Lower House for the seat of Boothby.

[9] Prior to Hill's retirement in 2006 he voted for legalizing the abortion drug RU486 which had been banned in Australia up until that point[10] As Liberal Government Senate leader Hill had expressed the importance of the transition of the Prime Ministership from Howard to his Liberal deputy and heir apparent Peter Costello be smooth.