Abstract A procedure to control all six DOF （degrees of freedom） of a UAV （unmanned aerial vehicle） without an external reference system and to enable fully autonomous flight is presented here. For 2D positioning the principle of optical flow is used. Together with the output of height estimation， fusing ultrasonic， infrared and inertial and pressure sensor data， the 3D position of the UAV can be computed， controlled and steered. All data processing is done on the UAV. An external computer with a pathway planning interface is for commanding purposes only. The presented system is part of the AQopterI8 project， which aims to develop an autonomous flying quadrocopter for indoor application. The focus of this paper is 2D positioning using an optical flow sensor. As a result of the performed evaluation， it can be concluded that for position hold， the standard deviation of the position error is 10cm and after landing the position error is about 30cm. Keywords Autonomous UAV， Quadrocopter， Quadrotor， Optical Flow， Positioning， Navigation