In genocide scholarship, dehumanization is often considered to be an alarming early warning sign for mass systematic killing. Yet, within broader research, dehumanization is found to exist in a variety of instances that do not lead to aggression or violence. This disparity suggests that while dehumanization is an important part of the genocidal process, it is too imprecise as a salient early warning sign. Genocide scholars have acknowledged such a conjecture in the past. This article initiates an embryonic research agenda that offers ‘toxification’ as a more precise early warning sign for genocide than dehumanization. It contends that while dehumanization signals that killing members of a particular group may be regarded as permissible, a more indicative early warning is one that flags when extermination is considered a necessity. Following a literature review of dehumanization, the purpose of this article is to introduce the idea of ‘toxificaton’, and to illustrate how the concept can work in practice, using two twentieth century genocides as examples.