Although rare and accounting for less than 1% of all breast cancers, the incidence of breast cancer in men has increased by 26% over the past few decades. Very little has been reported on the sonographic appearance of benign and malignant male breast conditions. The aim of this study was to describe the ultrasonographic features of male breast disease and the value of ultrasound in the evaluation of male breast disease. Between December 2006 and October 2014, ultrasound examinations were performed in 560 male patients presenting with enlargement of, pain in, and/or a lump in the breast. One hundred and thirty-six patients (24.3%) underwent surgical excision, and 424 patients (75.7%) were diagnosed by ultrasound. Their ultrasonographic features were retrospectively evaluated. The final diagnoses were gynecomastia (n=537), primary breast cancer (n=9), lipoma (n=7), chronic mastitis (n=6), and fibroadenoma (n=1). Of the 560 lesions, 356 (63.6%) were classified as Breast Imaging Reporting and Data System (BI-RADS) category 2, 191 (34.1%) were classified as BI-RADS category 3, and 13 (2.3%) were classified as BI-RADS 4 or 5. The sensitivity, specificity, PPV, NPV, and accuracy of the detection of malignant breast masses according to ultrasound were 100%, 99.3%, 69.2%, 100%, and 97.7% respectively. The sonographic patterns of gynecomastia were nodular (n=131, 24.4%), dendritic (n=50, 9.3%), and diffuse glandular (n=356, 66.3%). Color Doppler flow imaging revealed hypervascularity in five of these malignant masses, moderate vascularity in two of the masses, and mild vascularity in the remaining two masses. Other diseases included in the study are also described. Ultrasonography (US) is useful in the diagnosis of male breast diseases, especially in differentiating cancer from benign lesions.