Exotic animals can establish wild populations that may cause serious adverse economic and environmental impacts. In Australia, there are a number of species currently kept in captivity that would pose such threats were they to escape and establish. Paradoxically, there is a push to allow freer trade in animals between countries for recreational and commercial purposes. This paper considers approaches to assess and manage these risks, including the application of ecological theory to estimate the probability of escape, establishment, eradication, and harmful impact. Although some potential forms of impact are obvious, particularly for species that are pests in their natural or introduced range, others may be less so because species may change their behavior or ecology in new environments, and interact in unpredictable ways with resident plant and animal species. This uncertainty creates a need to leave a wide margin for error when assessing the risk of harmful impact.