This study was conducted to determine whether inflammation is present in the uvula mucosa of patients with obstructive sleep apnea (OSA). Uvulas were obtained by uvulopalatopharyngoplasty in 21 patients with moderate OSA (mean apnea/hypopnea index and standard error of the mean: 32 +/- 4) and by autopsy in 5 individuals not known to have OSA. Using point counting in five randomly selected high-power microscopic fields (X100), the authors found that the number of leukocytes in the lamina propria of the uvula mucosa was significantly higher in patients with OSA than in the controls (179 +/- 12 cells vs. 71 +/- 4 cells, respectively; P < .05). This was due to a significant increase in the number of plasma cells in patients with OSA as compared with controls (89 +/- 15 cells vs. 21 +/- 5 cells, respectively; P < .05). The thickness of the lamina propria (an index of interstitial edema) was also significantly increased in patients with OSA compared with controls (0.99 +/- 0.12 mm vs. 0.27 +/- 0.02 mm, respectively; P < 0.05). The authors conclude that inflammation, characterized by plasma cell infiltration and interstitial edema, is present in the uvula mucosa of patients with moderate OSA. They also suggest that soft palate inflammation contributes to upper airway occlusion observed during sleep in these patients.