This paper provides an overview of Data-Links for UAVs. Based on the functions, which have to he performed in different UAV missions, requirements for data-links are identified. After highlighting the basic variants of data-links and their general advantages and disadvantages a detailed discussion of some important design aspects is provided. Some real-world examples of data-links show how theory has been put to use, namely * Global Hawk SATCOM Data-Link as an example for an off-the-shelf solution. * HF Data-Link for Mucke UAV System as an example for the adaptation of MOTS hardware to a small UAV. * The BREVEL Microwave DATA-Link as an example for a solution to a specific requirement. The BREVEL Data-Link is one of the most advanced solutions available today. It was developed jointly between DaimlerChrysler Aerospace AG and MATRA SYSTEMS & Information until 1998 and is expected to go into production in Germany in 1999.