Urticaria is a common dermatological condition that can occur in acute and chronic forms. Common urticaria is generally easy to diagnose; however, urticarial syndromes should be considered in cases where lesions persist for greater than 24-36 h, the location of lesions has bilateral symmetry, urticarial lesions are accompanied by additional elementary lesions, and/or the patient presents with additional systemic symptoms. Additionally, urticarial syndromes should be considered for patients with typical urticarial lesions that do not respond to systemic antihistamine treatment. Hyperpigmentation or bruising can be observed following resolution of urticarial syndromes. Many cutaneous and systemic diseases can cause urticarial syndromes. Systemic causes of urticarial syndromes can afect multiple organ systems and may be accompanied by systemic symptoms such as fever, asthenia, and arthralgia. Clinicopathologic correlation is essential for the accurate diagnosis of urticarial syndromes. In this chapter, cutaneous and systemic etiologies of urticarial syndromes are reviewed.