A great number of species in the animal kingdom possess means by which they subdue prey or defend against predators. Human encounters with these species may result in bites or stings that produce local injury or systemic toxicity ranging from local pain and varying degrees of tissue injury to systemic illness, organ failure and even death. Most of these animals deliver a dose of venom when they bite or sting, but some produce or accumulate toxin in their flesh that may produce illness if ingested. Venoms are generally complex mixtures of proteins and enzymes, but few are very well understood. Antivenoms have been produced to treat exposures to some species, but treatment generally consists of supportive measures and treatment of symptoms. This chapter presents an overview of some of more common animal species found throughout the world, the toxic syndromes they produce and current therapeutic strategies.