How effective are large, well-resourced protected areas at achieving biodiversity conservation goals? In this study we critically review biodiversity research and management practice in two of the world's premier savanna reserves (Kruger National Park, South Africa and Kakadu National Park, Australia) by exploring management approaches to three shared conservation issues: fire, alien species and threatened species. These management approaches contrast sharply between the two reserves, with Kruger having notably more detailed and prescribed planning for biodiversity conservation. Overall assessment of the effectiveness of management is hampered by limited available information on trends for native species and threatening processes, but in general it is far more straightforward to understand the management framework and to measure biodiversity conservation performance for Kruger than for Kakadu. We conclude that biodiversity conservation outcomes are most likely to be related to the adequacy of dedicated resources and of monitoring programs, the explicit identification of clear objectives with associated performance indicators, and the considered application of management prescriptions. In Kakadu particularly, conflicting park objectives (e.g., biodiversity and cultural management) can reduce the effectiveness of biodiversity efforts. However, we recognize that for the long-term persistence of these large conservation areas and hence for biodiversity conservation, it is critical to include consideration of social context. © Springer Science+Business Media B.V. 2009.