Background: Identification and localization of functional lymphatic vessels are important for lymphaticovenular anastomosis. Conventional high-frequency ultrasound (CHFUS) has been reported to be useful for them, but it has some disadvantages. In this article, we present new capabilities of ultra high-frequency ultrasound (UHFUS) for imaging of the lymphatic vessels, which may overcome the weakness of CHFUS. Methods: Thirty unaffected extremities in 30 unilateral secondary lymphedema patients (13 upper limbs and 17 lower limbs) were examined. Identification of the lymphatic vessels using UHFUS and CHFUS were performed at 3 sites in each unaffected extremity. Number and diameter of the detected lymphatic vessels were compared between UHFUS and CHFUS groups. At the same time, new characteristics of the lymphatic vessels seen with UHFUS were investigated. Results: One hundred sixty-nine lymphatic vessels were detected with UHFUS, and 118 lymphatic vessels with CHFUS. The number of lymphatic vessels found in upper and lower extremities was significantly larger with UHFUS than with CHFUS. The diameter of lymphatic vessels found in upper and lower extremities was significantly smaller with UHFUS than with CHFUS. All lymphatic vessels that were detected in UFHUS were less likely to collapse when the transducer was against the skin of the examined sites. Conclusions: Detection rate of the lymphatic vessels in nonlymphedematous extremities with UHFUS was higher than that with CHFUS. UHFUS provides images with extremely high resolution, demonstrating new characteristics of the lymphatic vessels.