OBJECTIVES: To validate the Spanish version of the UAS, the most widely used patient-reported outcome measure for patients with chronic idiopathic urticaria (CIU), and its administration over 7 consecutive days (UAS7). METHODS: Observational, prospective, multicentre study in adult patients with CIU. The UAS has 2 items (intensity of pruritus and number of hives, scored 0-3) and ranges from 0-6 (lowest to highest disease activity). The UAS7 is the sum of UAS over 7 consecutive days. Both scales were completed at baseline and after 6 weeks, together with health-related quality of life (CU-Q2oL and EQ-5D) and disease severity (Clinician (CRS) and Patient Rating Scale (PRS); Clinician (CRSC) and Patient Rating Scale of Change (PRSC)) questionnaires. RESULTS: CONCLUSIONS: The Spanish versions of UAS and UAS7 scales are valid, applicable and reliable tools to assess disease control in the clinical practice in patients with CIU. A 4-5 point change on the Spanish UAS7 might be interpreted as an important difference.