As ideas about effective conservation of biodiversity develop, zoos are adapting their roles to meet the new challenges. This article considers these changes, using the work of Bristol and other UK zoos as a case study. The significance of zoos in both global and local conservation of biodiversity, their role in promoting public engagement and mass action, and their increasingly important role in formal education are discussed, all in terms of driving the changes urgently needed to ensure a sustainable future. (Contains 15 figures.)