This review article is based on the lecture given by Professor Metreweli about the application of ultrasound for head and neck masses at the Department of Otolaryngology, National Taiwan University Hospital (NTUH), on March 17, 1995. Professor Metreweli is the chairman of the Department of Diagnostic Radiology and Organ Imaging, Prince of Wales Hospital, the Chinese University of Hong Kong. He was invited to Taiwan by the Department of Radiology, NTUH. Ultrasound is a noninvasive, repeatable, and convenient tool in the diagnosis of head and neck masses, however, the specificity is quite doubtful, especially when the age factor is taken into consideration. In clinical assessment, no single echographic characteristic could be pathognomonic to distinguish benign from malignant lymph nodes, thus we should also consider the clinical findings and the results of fine needle aspirations.