A look at the latitudinal gradient from North America via South America to Antarctica supports the impression that the ecosystems of this part of the world provide perfect conditions for marine biodiversity studies. Several bilateral or international initiatives with major German contributions have focused on biodiversity questions, especially in South America and Antarctica. At depths > 50 m accessible to shipboard sampling, an oxygen minimum zone (OMZ) prevails off Peru and Chile (except in the extreme south). The macrobenthic biota associated with the OMZ are extremely poor but show a gradient of increasing diversity at great depths and towards the south. In the southern Chilean fjords and channels, habitat heterogeneity is high and differences in the fauna can be observed over even small distances, especially in the Magellan area. A high intra-habitat biodiversity can, thus, be expected. On the exposed deep shelf around Antarctica, a large-scale gradient between a community dominated by a very high biomass and abundance of sessile suspension feeders can be distinguished from a community with significantly fewer epifauna. However, their relationships to the environmental conditions are still poorly understood. For the future, two approaches are recommended, the study of zoogeographical questions in the light of evolution and the identification of the key processes, including environmental changes, that engender biodiversity patterns.