District Officer, Hulu Langat; Principal Assistant Secretary, Economic Planning Unit, Prime Minister's Department and Deputy State Secretary, Selangor. He was the Minister of Welfare Service from 1984 to 1986, the Minister of Federal Territory from 1986 to 1987, the minister of Foreign Affairs from 1987 to 1991, the Minister of Domestic Trade and Consumer Affairs from 1991 to 1997 and the Menteri Besar of Selangor from 1997 to 2000. He was Member of Parliament (Kuala Selangor) from 1978 to 1997 and Selangor State Assemblyman (Permatang) from 1997 to 2004. He is now a member of the Council of the Royal Court Selangor (Dewan DiRaja Selangor), Pro-Chancellor of Universiti Industri Selangor (UNISEL) and President of Majlis Bekas Wakil Rakyat (MUBARAK), Selangor.

         Tan Sri Dato' Seri (Dr) Haji Abu Hassan is currently Chairman of Basis Holdings Sdn. Bhd. He also serves as chairman, advisor and director of several public and private limited companies. Amongst them are as chairman of OILFAB Sdn. Bhd., Advisor of Twinners (M) Sdn. Bhd, Director of LSB Bina Group Bhd. He is also Patron, Chairman and President of a number of Non-Governmental Organisations. Amongst them are as Patron, Univertisy of Hull Alumni; Patron, Rumah Tunas Harapan Tengku Ampuan Rahimah, Kuala Selangor, Patron Persatuan Bekas Murid Murid, Sekolah Tinggi Klang, Selangor; Advisor of Royal Klang Club; Chairman of Board of Trustees Mental Health Foundation, Malaysia and Chairman of Derma Alam Shah Committee. In Kota Kemuning, Shah Alam where he resides, he is Patron of the Kota Kemuning Residents' Association, and Patron of Surau Al-Hijrah and As-Solehin.