Venomous and poisonous animals are a significant cause of global morbidity and mortality. This Seminar will cover selected aspects of these animals, their venoms/poisons, and their clinical impact on humankind, from a global perspective, but with a distinctive Australian flavor and a clinical emphasis. Venomous snakes are found throughout most of the world, including many oceans, and have evolved a variety of highly effective toxins and methods of delivery. Their impact on humans is considerable, most current data suggesting they cause in excess of 3 million bites per year with more than 150,000 deaths. Particularly in the rural tropics, snakebite morbidity and mortality has a significant human medical and economic toll. The major groups of snakes causing bites are the vipers, the elapids (cobra type), the sea snakes, the side-fanged vipers, and the back-fanged colubrids. Australian venomous snakes are nearly all elapids and have evolved some of the most toxic of all snake venoms. Their effects include potent procoagulants and anticoagulants, neurotoxins, myotoxins, and nephrotoxins, but a distinct absence of the major local necrotoxins found in some non-Australian elapids and many vipers. The effect of these toxins on humans is not limited to envenoming, for the toxins are proving invaluable as research tools and diagnostic agents, and may even have a future as precursors of therapeutic agents. Because of the high toxicity and diversity of Australian elapids, a variety of monovalent antivenoms have been developed. There is also a venom detection kit to determine the type of snake and allow targeted antivenom therapy. The kit has also increased information available on diagnostic patterns of envenoming for each species. Australia is also home to the world's most lethal spiders, the funnel webs of eastern Australia, as well as the red back spider, the single most common reason for antivenom treatment in Australia. The latter spiders have been accidently exported to Japan. Within the marine environment exist a vast array of toxic animals, both poisonous and venomous, which not only cause morbidity and mortality in humans, but offer an incredibly rich array of valuable toxins. Australian waters contain some of the most lethal and medically problematic species, presenting a diverse range of clinical problems.