In 1991, we have developed a needle insertion robotic system for CT-guided stereotactic neurosurgery. The system, based on existing stereotactic frame, had six DOF of movement with minimum size to fit a CT gantry.Safety issue was carefully considered: by cutting off the power supply, all axes were held rigidly to avoid unexpected motion. A phantom study using X-ray CT showed that the overall position error was 1.0mm. This system was followed by MRI-compatible version.This paper presents the history of this system and briefly reviews other stereotactic robots.