Ultrasonographic findings that have been reported in chronic inflammatory demyelinating polyneuropathy (CIDP), include enlargement of cervical nerve roots, diffuse nerve enlargement, and enlargement corresponding to sites of conduction block (but this is not universal). Similar findings are reported to occur in acute inflammatory polyradiculoneuropathy and multifocal motor neuropathy. However, ultrasound has not been studied as extensively in these disorders. Demyelinating hereditary polyneuropathies (Charcot-Marie-Tooth type 1 and hereditary neuropathy with liability to pressure palsies, in particular) are associated with profound enlargement of peripheral nerve cross-sectional area on ultrasound, whereas axonal hereditary polyneuropathies, such as Charcot-Marie-Tooth type 2, show only modest nerve enlargement. Only a few studies have used ultrasound to examine the nerves of those with diabetic polyneuropathy, and it is not clear if reproducible ultrasonographic nerve findings can be seen in this population. The role of ultrasonography in the assessment of polyneuropathy remains less well defined. This article briefly reviews the existing literature on ultrasonography in neuropathy along with its implication for diagnosis, treatment, and prognosis. Key Words: Ultrasound, Polyneuropathy, Acquired, Hereditary