High-frequency ultrasound diagnostic equipment (HFUS) using probes with frequencies above 15-MHz has been utilized conventionally in preoperative assessments and postoperative follow-up of skin tumors. The advent of probes with even higher frequencies (up to 30-MHz) has widened the clinical applications of HFUS to inflammatory dermatoses which are histologically confined to the epidermis and upper dermis, such as psoriasis and atopic dermatitis. Ultrasound imaging has the advantage of being a noninvasive and relatively inexpensive technology that is quick and easy to perform. In addition, information obtained from HFUS is unique and useful for clinical diagnosis and evaluation for various skin disorders. We believe that HFUS has the potential to become a powerful tool for either clinical or investigative dermatology. Herein, we present a case of lichen sclerosus et atrophicus (LSA) to which we applied HFUS before skin biopsy and obtained substantial information for the differential diagnosis from morphea, and we reemphasize the usefulness of HFUS in studying the inflammatory skin disorders.