Reliable information is the foundation upon which local, national and international conservation efforts are based, placing research at the heart of biodiversity conservation. The fundamental role of research is diverse and includes understanding the importance of biodiversity, defining 'units' of biodiversity, priority-setting for species and sites, managing endangered and declining populations, understanding large-scale processes, making predictions about the future, and interfacing with training, education, public awareness and policy initiatives. Using real examples, researchers consider the principles underlying these manifold issues and illustrate how these principles have been applied to address actual conservation problems.