This paper examines the risks that contemporary chemical, life and associated scientific research and technological developments could be miused for the weaponization of mid-spectrum agents—toxins, bioregulators, and other substances of biological origin, and their synthetic analogues. Drawing on illustrative case studies of dual use research and related activities of potential concern from China, India, Iran, Russia, Syria and the United States, it discusses how States can ensure such research and related activities are not utilized in weapons development. Although midspectrum agents are, in theory, covered by both the Biological and Toxin Weapons Convention (BTWC) and the Chemical Weapons Convention (CWC), this apparent overlap in reality masks a dangerous regulatory gap—with neither Convention implemented effectively to address threats of weaponization of these agents. The paper highlights the potentially damaging consequences of this failure for international peace and security, and proposes realistic routes for action by the BTWC and CWC State Parties to address these challenges.