An ecosystem approach for the management of human activities in the Southern Ocean is enshrined in the principles of the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR). The implementation of such an approach requires an understanding of the wider dynamics of the ecosystem, which is best achieved through the development of ecosystem models. However, not all models will be suitable for developing an ecosystem approach to management. To facilitate the development of ecosystem models appropriate for CCAMLR, we review the existing models of Southern Ocean ecosystems that include krill and the higher trophic levels. We also briefly consider modelling approaches from elsewhere in the world. The main categories we consider are models of krill populations and life cycles, predator-prey models and models of ecosystems. A range of approaches has been developed in each of these categories and we review the major results of each approach. Finally, we discuss the issues highlighted by the studies that are still relevant today, and we note where major requirements for model development were identified.