Indoor Positioning Systems (IPS) have lead to increased e ciency in many types of organizations and industries, and more and more companies embrace the new opportunities and functionality found in IPS solutions. Because of IPS's importance and usage potential in creating new services, there is a signi cant interest in the industry for IPS and Real Time Locating Systems (RTLS). The market potential for companies that develop and sell IPS and RTLS systems are thus predicted to be large in the coming years. An IPS system may consist of only one technology, or be a hybrid of two or more technologies. Although the biggest di erence between IPS systems are the technology they are based on, it is often the performance, usage, ease of deployment, cost, or a combination of these, that matters. Examples of technologies that are used in IPS systems and assessed in this thesis are Radio Frequency Identi cation (RFID), Wi-Fi, Ultrasound and Ultra-Wideband (UWB). The technology assessment showed that UWB is probably the best technology for use in indoor positioning systems. Ultra-Wideband is however in its early phases and are therefore not regulated for use in all countries, for instance Norway. Wi-Fi is on the other hand a good choice for open indoor environments such as o ce or class rooms where some level of positioning error is accepted as long as the decreased performance is reflected in the price of the system. The testing program build in this thesis, including the proposed positioning methods, show that it is possible to create a low cost indoor positioning system by re-using the existing wireless network infrastructure and still achieve an acceptable level of accuracy.