Dr Horst Reeps was born in Straubing, Germany in 1947. After completing a Master's degree in Chemistry and Chemical Engineering in 1973, receiving his Dr. rerum naturalis (PhD) in Organic Chemistry and Spectroscopy in 1976, Dr Reeps then taught Organic Chemistry at the Technical University in Munich until 1977.

Dr Reeps then conducted research as an officer of the German Bundeswehr (German Army) in NBC defence, chemical health and safety, chemical synthesis, as well as the threat assessment and threat reduction of weapons of mass destruction from 1977 until his transfer to the German Federal Foreign Office in 1993.

In 1993, Dr Reeps was appointed as the head of the Chemical Team of the United Nations Special Commission (UNSCOM) responsible for disarmament and industry verification in Iraq.

With his transfer to the Permanent Mission of the Federal Republic of Germany to the United Nations in 2000, Dr Reeps acted as Scientific Adviser, Disarmament and WMD, Special Projects and Liaison Officer to UNMOVIC (The United Nations Monitoring, Verification and Inspection Commission).

During 2001, Dr Reeps was appointed to the Directorate-General for Disarmament and Arms Control of the Federal Foreign Office as an adviser on weapons of mass destruction. In 2002 Dr Reeps became Director of Verification of the OPCW.