Background: Ultrasonography (US) has recently proved to be useful in diagnostic dermatology. It is convenient to use, completely safe, and provides valuable information., Objective: This study was performed to compare the diagnostic accuracy of US with that of clinical diagnosis in patients with benign subcutaneous lesions., Methods: We retrospectively examined data for 100 patients with benign subcutaneous lesions who were diagnosed with US and either biopsy or surgery at Seoul National University Boramae Hospital between January 2010 and May 2013., Results: Ultrasonography significantly increased the diagnostic yield of benign subcuta-neous lesions (after physical examination [PE], 52.0%; after US, 82.0%; P < 0.005). Rates of sensitivity and specificity for the diagnosis of lipoma were 61.5 and 92.0%, respectively, after PE, and 100 and 100%, respectively, after US. Rates of sensitivity and specificity for the diagnosis of epidermal cysts were 69.4 and 78.4%, respectively, after PE, and 91.8 and 92.2%, respectively, after US. Additionally, rates of sensitivity and specificity for pilomatrixoma were 12.5 and 98.9%, respectively, after PE, and 75.0 and 100%, respectively, after US. Although the accuracy of diagnosis of vascular anomalies and nerve sheath tumors was increased after US, the difference was not significant (vascular anomalies: 40.0% after PE and 80.0% after US; nerve sheath tumors: 28.6% after PE and 42.9% after US)., Conclusions: This study suggests that US is a simple and reliable tool that can aid the diagnosis of benign subcutaneous lesions., (© 2015 The International Society of Dermatology.)