Objectives. To evaluate fraction of exhaled nitric oxide (F E NO 50 ) and deaerated exhaled breath condensate pH (dEBCpH) as non-invasive markers of subclinical airway inflammation in pediatric patients with rheumatologic disorders.Methods. We determined F E NO 50 and dEBCpH in a prospective study spanning at least 12 months, comprising 85 pediatric patients with rheumatologic disorders, including juvenile idiopathic arthritis (JIA, n=63), chronic recurrent multifocal osteomyelitis (CRMO, n=6), systemic lupus erythematosus (SLE, n=3), juvenile dermatomyositis (JDM, n=1) and other rheumatic disorders (n=12). dEBCpH was determined once in a group of children without evidence of rheumatologic or pulmonary disease (controls, n=90). Findings were correlated with results of pulmonary function tests. Atopic sensitization was assessed by RAST or skin prick test in 76 patients.Results. Atopic sensitization was detected in 34% (26/76) of patients. Neither F E NO 50 nor dEBCpH correlated with disease activity, but intermediately (20-35 ppb) or highly elevated (>35 ppb) levels were observed at least once in 26 patients (31%), 19 of whom had atopic sensitization. Median dEBCpH did not differ between cases and controls (8.05 vs. 8.02; p=0.48). Median dEBCpH decreased slightly over the study period (p=0.02), whereas F E NO 50 values did not change significantly (p=0.89). There were several patients with significantly abnormal dEBCpH values that could not be readily explained by diagnosis, higher disease activity, medications, or atopic sensitization.Conclusions. There were no consistent abnormalities in F E NO 50 or dEBCpH in this cohort of Caucasian patients with relatively stable rheumatologic disorders, but there were some patients with abnormal values of unknown significance.