The protein pore-forming delta-endotoxins from the bacterium B. thuringiensis have long been known for their insecticidal activity and have been used commercially as insecticides, either in sprayable form, or expressed in transgenic crops. One great advantage of these toxins is that they show a high degree of specificity and so can be used to target particular pests without affecting non-target insects such as pollinators or natural predators. More recently a subclass of these toxins have been discovered that have to ability to kill human cancer cells – again with a high degree of specificity. Not only do these target only a limited range of cells, but also do not seem to affect non-cancerous ones. One disadvantage of the tight specificity though, is the difficulty in finding toxins effective against a particular pest insect. As a result many labs, including my own, have been attempting to understand what determines the host range of a particular toxin and using that knowledge to retarget toxins towards different host insects or cells. In this presentation I will give an overview of our current understanding of these toxins and describe how they are being used commercially. I will then move on to consider in detail the interactions between toxin and host that can affect susceptibility before moving on to methods for altering host specificity. I will also cover potential applications of this research in targeting recalcitrant insects, overcoming evolved field resistance and their potential for cancer therapeutics.