Robots have been introduced to the operating room primarily to provide higher accuracy and dexterity. Mechatronic devices can support surgeons with advanced targeting, visualization and task execution with a precision beyond the human skills. To evaluate a system, accuracy tests are required, and proper methodology should be applied to describe its properties. It is crucial in interventional medicine to test the application accuracy of a system, showing the overall task execution error. This may be a non-linear function of the intrinsic- and registration accuracies, as described in the paper. Different methods are presented to provide system characteristics. Also, the most important surgical robot systems are introduced in details along with their published accuracy measures. Despite the fact that the added value of a surgical robot is usually consistent with the precision it can achieve, the importance of overall safety, predictability and transparency many times overcomes the need for spatial precision.