In the teleprogramming system an operator is presented with a virtual reality representation of a remote environment. The operator's interaction within that virtual environment is observed and translated into a sequence of robot program instructions for transmission to, and execution by, a robot at the remote site. In this paper we focus on operator interaction with the master station of the teleprogramming system. The use of synthetic fixtures to provide force and visual clues to assist the operator in performing tasks with speed and precision is discussed. It is suggested that, at least in some situations, it is both necessary and desirable to trade off realism for improved task performance. The difficulty of coping with exceptional conditions and, in particular, uncertainty in the world model used to generate the virtual environment is described and the operator interface for diagnosing and resolving errors is presented. An overview is also given of both the hardware and software used to implement the master station for the teleprogramming system.