This paper provides a chronological record of the history of poison in vertebrate species control in south-east Australia, since the first instance was recorded to target dingoes in 1814. Over this time, poison was employed first as a weapon against native wildlife, and then as a curative to address Australia's increasing biodiversity crisis. The paper examines this paradox, and the legacy of Australia's long-term pairing of toxicology and environmental management. The institutionalisation of poison describes the process whereby the use of poison has become normalised and supported by services and systems embedded within a political, legal and social framework. Poison was found an effective tool for clearing lands selected for agricultural production in the early 1800s, and this discovery was followed by a rapid expansion in the application, range, methods of delivery and quantity of poison/poisoned baits applied. Campaigns were targeted towards an increasing number of declared species, and eventually the technology took to the sky in 1947. No region was then beyond the reach of the pest control agencies. Agricultural expansion in partnership with use of broadspectrum poisons has transformed the Australian environment. I argue that the marginalisation and local extinction of numerous native species, can be traced directly back to this industrial catalyst. However, toxicology has taken on a new fight in the 21st century, with poisoned baits reassigned towards the restoration of native ecology, in a program described as “chemotherapy for the environment” (Marks 2013). The science of toxicology now targets alien terrestrial vertebrate species believed to be responsible for the biodiversity crisis. This paper examines the historical processes that led to this institutionalisation of poison, followed by many irreversible environmental disruptions and extinction events.