Disorders of peripheral nerves are usually diagnosed by neurological examination and electrodiagnostic methods. However, we can investigate peripheral nerves also by imaging methods, particularly by ultrasonography. During ultrasonographic examination we are particularly interested in nerve cross sectional areas that are often enlarged at entrapment or compression points in focal neuropathies and in demyelinative polyneuropathies. Ultrasonography is established method for diagnosing focal neuropathies: median nerve at the wrist, ulnar at the elbow, posterior interosal at the supinator muscle, fibular at the fibular head, lateral cutaneous nerve of the thigh. It is very useful also in patients with clinical and electrodiagnostic signs of complete nerve lesion, particularly due to trauma, where nerve transection cannot be ruled out. In rare patients ultrasonography can diagnose also progressive peripheral nerve lesion due to expansive lesion. It is also useful in diagnosing demyelinative polyneuropathies, both hereditary (e.g., Charcot-Marie-Tooth disease 1A) or acquired (e.g., chronic inflammatory demyelinating polyneuropathy). Likewise, it enables guided infiltrations in the region of nerve. Ultrasonography introduced a new, morphologic dimension in neurology of peripheral nerves that can significantly improve management and outcome in selected patients.