Since we first successfully performed magnetic resonance (MR)-guided microwave coagulation therapy for liver tumors in January 2000, we have developed new MR-compatible instruments, laparoscopy and thoracoscopy, which have enabled us to approach liver tumors located just below the diaphragm and in contact with other organs. We have customized software for an MR gradient-based tracking system for the easy detection of the location and orientation of treatment area and for the real-time display of MR temperature maps with a scale bar. Navigation software was customized to enable real-time image navigation. The reformatted images in the two perpendicular planes complemented the limitations of real-time MR imaging. Evaluation software, "FootPrint," was useful for distinguishing treated areas from untreated areas and improved the evaluation of treatment accuracy. These newly developed MR-guided systems that utilize microwave have played important roles in more accurate, safer, and easier treatment for liver tumors. We have treated 184 patients using these new techniques without major complications.