The applications of ultrasonography (US) in oncology have rapidly increased during the past few years. Technical improvements, development of new technologies, easy availability, and non-invasiveness are some of the reasons for the rapid diffusion of US. Nowadays a large number of malignancies, both superficial and deep-seated, can be examined by US. In order to give an overview of the present role of US in oncology it is necessary to discuss many different topics including tissue characterization, diagnostic role, staging, follow-up and future developments.