In context of this bachelor thesis "indoor positioning with ultrasonic and radio", a current research and development area was handled. The aim of this study was to develop a system that can determine the position of a device with an accuracy of about 10 cm.\par In one room 3 to 6 reference nodes are positioned, which are radio-controlled by a master reference node. The master reference node coordinates the transmission of ultrasonic localization signals by each reference node and the distance measurements of all receivers (blind nodes). Each blind node receives the ultrasonic signals from the reference nodes and calculates the distance to them by time of flight. With the broadcasted position data of the reference nodes on radio, a blind node can compute its own position (like GPS). In this way, any number of blind nodes can operate independently in a room.\par In order that a blind node is able to determine the distances to the reference nodes correctly, there must be ensured that no other localization signal is received, that could interfere. To achieve this, the reference nodes are separated from each other by TDMA. Rooms can be separated from each other by using CDMA. A spread spectrum-modulation and -demodulation of the ultrasonic localization signals ensure a sufficient interference resistance to noise effects. As part of the problem analysis, a suitable system was evaluated. Further, the hardware and software for the blind- and reference nodes have been developed, manufactured and tested. The radio link between the nodes and the ultrasonic distance measurement are working in the required scale. The same applies for the position calculation. The system achieves the required accuracy of 10 cm, which can be mainly affected by not compensatable temperature differences in the room. The expectations of the present bachelor study were met.\par The blind node can show its own position as well as all measured distances on its display. A serial interface of the blind node also enables evaluation and representation of the blind node position in a specially developed program on a computer.\par An integration of the blind node in a mobile device, such as a smart phone is also possible. With microphone, antenna and display, it would be perfect for commercial in future applications.