Image-guided procedures are very common and useful for achieving precise and safe minimally invasive surgery with limited visual information. Surgical navigation systems provide surgeons with quantitative and subjective guidance information in minimally invasive treatment. The most critical problem associated with surgical navigation systems is how to deal with soft organ deformation and motion during surgery, and intraoperative imaging is one solution to this problem. Ultrasound imaging is one of the most promising imaging modality as it is commonly and easily usable in a treatment environment, is cost-effective, and has high-speed scanning ability compared with CT and MRI. While many 2D ultrasound image navigation systems have been developed for laparoscopic surgery, we have developed a real-time 3D ultrasound navigation system for fetal endoscopic surgery. We are also developing new procedure called water-filled laparoendoscopic surgery (WaFLES), with which we can obtain 3D real-time and wide ultrasound images during surgery. As for the future of image-guided minimally invasive surgery, intraoperative ultrasound imaging will be a leading technology, and it will be required to make new innovations in both surgical procedures and medical device technologies with medicine-engineering collaboration and seeds-needs matching.