Objective: To develop and test the validity of a qualityof-care performance measure that examines antibiotic prescribing rates in children diagnosed as having upper respiratory infection (URI) or bronchitis. Design and Methods: The measure developed examines the annual rate of antibiotic prescribing to children aged 3 months to 18 years with an episode of URI or bronchitis. Administrative data from 5 US health plans were used to identify episodes of URI or bronchitis using International Classification of Diseases, Ninth Revision, codes 460, 465, 466, and 490. Pharmacy data (National Drug Codes)-were used to determine whether antibiotics were prescribed for the URI or bronchitis episode. Medical record abstractions were performed on a random sample of 465 cases to assess percentage agreement with pharmacy claims data for antibiotic prescribing. Results: For the 84 166 children and adolescents aged 3 months to 18 years who had at least 1 episode of URI or bronchitis during the measurement year, 31% received antibiotics. Prescribing rates for URI and/or bronchitis varied widely among the 5 participating health plans (2% -75% ; P < .001). Inappropriate antibiotic prescribing occurred most frequently for bronchitis episodes, with 4 of 5 health plans prescribing antibiotics in 60% of such cases (range, 60% -80% ). Percentage agreement between administrative and medical records data for antibiotic prescribing was 88% . Conclusions: This quality measure is feasible to implement at the health plan level and validly assesses antibiotic prescribing rates using administrative data. Improvements in adhering to judicious use guidelines for antibiotic prescribing in children with URI and bronchitis are warranted. Objective: To develop and test the validity of a qualityof-care performance measure that examines antibiotic prescribing rates in children diagnosed as having upper respiratory infection (URI) or bronchitis. Design and Methods: The measure developed examines the annual rate of antibiotic prescribing to children aged 3 months to 18 years with an episode of URI or bronchitis. Administrative data from 5 US health plans were used to identify episodes of URI or bronchitis using International Classification of Diseases, Ninth Revision, codes 460, 465, 466, and 490. Pharmacy data (National Drug Codes) -were used to determine whether antibiotics were prescribed for the URI or bronchitis episode. Medical record abstractions were performed on a random sample of 465 cases to assess percentage agreement with pharmacy claims data for antibiotic prescribing. Results: For the 84 166 children and adolescents aged 3 months to 18 years who had at least 1 episode of URI or bronchitis during the measuremen t year, 31% received antibiotics. Prescribing rates for URI and / or bronchitis varied widely among the 5 participating health plans (2% -75%; P <.001). Inappropriate antibiotics prescribing occurred most frequently for bronchitis episodes, with 4 of 5% of health plans prescribing antibiotics in 60% of such cases (range, 60% -80%). Percentage agreement between administrative and medical records data for antibiotic prescribing was 88%. Conclusions: This quality measure is feasible to implement at the health plan level and validly asses antibiotic prescribing rates using administrative data. Improvements in adhering to judicious use guidelines for antibiotic prescribing in children with URI and bronchitis are warranted.