Some snakes lineages have evolved specialised venoms. These represent a fascinating model of protein evolution under strong selection. We have sequenced and analysed the genomes of a number of snake species. Major toxic components of the venom, such as three finger toxins, have undergone massive duplication after recrutiment to the venom gland through a variety of mechanisms. Interestingly, we also find that venomous snakes are not only engaged in an arms race against their prey by evolving new toxins, but they may also be in an arms race against bacteria in the venom gland. Future prospects include the study of developmental changes in venom protein composition during the lifetime of individual snake as they switch from small arthropod prey to larger rodent prey. This type of study requires a new generation of bioassays for studying venom bioactivity with low volumes and without using mammalian models. We have developed specialised assays based on zebrafish embryos.