INTRODUCTION: Levels of C-reactive protein (CRP), an important serum marker of inflammation with major implications for cardiovascular morbidity and atherogenesis, are elevated among adult patients with sleep-disordered breathing (SDB). We hypothesized that elevated CRP plasma levels would also be present among children with SDB. METHODS: Eighty-one children (mean age: 9.3 +/- 3.7 years) underwent polysomnographic evaluations. Samples for plasma CRP level and lipid profile determinations were drawn the next morning. RESULTS: Because plasma CRP levels were not normally distributed in this cohort, logarithmic transformation was applied. Log plasma CRP levels were significantly higher in the SDB group (obstructive apnea/hypopnea index [AHI] of > or =5), compared with the mild SDB group (AHI of > or =1 and <5) and the control group (AHI of <1). Significant positive correlations were found between log CRP levels and AHI (r =.53) and arousal index (r =.28), whereas an inverse correlation was found between the lowest nocturnal arterial oxygen saturation and log CRP levels (r = -.47). These correlations persisted after exclusion of outliers. Moreover, 94% of the children with elevated log CRP levels reported excessive daytime sleepiness and/or learning problems, compared with 62% of the children with normal log CRP levels. CONCLUSIONS: Plasma CRP levels were increased among some children with SDB and were correlated with AHI, arterial oxygen saturation nadir, and arousal index measures. These changes were particularly prominent among children who were sleepy or presented with neurobehavioral complaints. The intermittent hypoxemia and sleep fragmentation of SDB may underlie inflammatory responses, the magnitude of which may ultimately lead to the cardiovascular, cognitive, and behavioral morbidities of SDB.