As this book often makes clear, in situ conservation is the favoured approach to CWR conservation, as it has the distinct advantage that target species are continuously exposed to a changing natural environment that allows new diversity to be generated. However, such exposure can often dramatically threaten the very existence of these species. For this reason, in situ conservation approaches will often need to be supported by complementary conservation approaches for the sake of security. Such complementary conservation approaches also have the advantage that they help facilitate access by plant breeders to important genetic materials for crop improvement. Some level of complementary conservation will need to be practised for the optimal conservation of CWR. It is beyond the scope of this manual to provide an in-depth examination of the various complementary conservation approaches available for CWR. Moreover, it is the aim of this chapter to provide the reader with a general overview of the types of approaches and techniques that are available and to highlight how these might be used to complement in situ conservation, such as the provision of a safety net for genetic diversity, which is difficult to conserve in situ or threatened in the wild. Further, the potential role of ex situ collections in facilitating the recovery and reintroduction of CWR populations in situ is highlighted.