Abstract： Objective To evaluate the plasma levels of adrenomedullin (ADM) and urotensin Ⅱ ( U-Ⅱ ) in children with capillary bronchiolitis, and their clinical significance. Methods One hundred and fifty three children with capillary bronchiolitis and 36 healthy children were recruited. Plasma levels of ADM and U- Ⅱ were measured at acute stage ( <7days) and convalescent stage (>14days) of airway inflammation. The relationship of plasma ADM and U-Ⅱ levels with symptom scores was evaluated. Results Plasma levels of ADM and U-Ⅱ in acute stage of capillary bronchiolitis were significantly higher than those in convalescent stage and healthy controls ( ADM: t = 20. 57 and 26. 26, P < 0. 01; U-Ⅱ: t = 14. 27 and 7. 61, P < 0. 01 ) , and there were significant differences among mild, moderate and severe capillary bronohiolitis (F = 245. 94 and 304. 79, P <0. 01). Plasma level of U-Ⅱ in convalescent stage of capillary bronchiolitis was lower than that of healthy controls (t = 6. 99, P <0. 01 ) , but ADM was still in a higher level ( t = 8. 98, P < 0. 01 ). In the convalescent stage, there was significant difference on U-Ⅱ levels among mild, moderate and severe capillary bronchiolitis ( F = 25.69, P < 0. 01 ) , but no significant difference was observed for ADM levels (F = 2. 25 , P > 0. 05 ) . Plasma levels of ADM and U- Ⅱ in acute stage showed positive correlation with symptom scores, and the regression coefficients were 0.884 (P =0. 000) for ADM and 0. 943 (P = 0. 000) for U-Ⅱ . Conclusion Plasma ADM and U-Ⅱ levels in children with capillary bronchiolitis are increased in acute stage and correlated with the symptom scores, which may serve as laboratory indicators for assessing the severity of the disease.