The Dermatology Life Quality Index (DLQI) was designed to be used with different types of dermatologic pathologies instead of being directed at a single condition such as psoriasis or acne. Although a reasonable approach, this broader measurement model may not be appropriate for conditions such as chronic idiopathic urticaria (CIU) that, unlike some other chronic skin conditions, are subject to daily or weekly fluctuations. OBJECTIVES: This validation study tested the reliability, structural validity, and construct validity of the DLQI in two samples of CIU patients obtained from two large identical multicenter, double-blind, randomized, placebo-controlled, parallel studies. METHODS: Patients recorded daily signs and symptoms (# of wheals and pruritus severity) on a daily basis, and completed the DLQI during three clinic visits (approximately 2 weeks apart); investigators also assessed CIU severity. RESULTS: The DLQI means and standard deviations indicated relatively symmetrical distributions free from serious ceiling or floor effects, and alpha coefficients indicated an acceptable level of reliability in the two samples. The exploratory factor analysis suggested that the six categories of items did not define different factors and supported the unidimensionality of the scale. In a formal test of the structural validity for a single-factor model, confirmatory factor analysis supported either a one or two-factor model, with the correlations from the two-factor model indicating that the total score of all items is interpretable as a global score. Item response analyses showed that most items were able to distinguish people with low versus high impairment at the appropriate ends of the continuum demonstrating content validity. Finally, changes in DLQI scores were related to changes in investigator and patient-assessed symptoms of urticaria, providing evidence of construct validity. CONCLUSION: These results support the DLQI as a valid instrument for the measurement of CIU related quality of life.