The reach of Sec. 10(3) of the German Patent Act (GPA) has been the subject of debate by German patent courts for many years. Final clarification by the German Supreme Court is still awaited on the extent to which third parties are liable for their own supplying acts which do not themselves fall under one of the privileged provisions of Sec. 11 Nos. 1 to 3 GPA. This poses considerable legal risks for both suppliers and recipients, which are particularly evident in the pharmaceutical sector in the context of privileged acts covered by Sec. 11 No. 2 or No. 2b GPA. The article from Dr Marco Stief and Tobias Matschke explores the history of the legal provision, examines the approaches taken in the German literature and case law on the subject to date, and discusses possible contractual and practical measures to reduce the liability risk.