Abstract： Objective To investigate the expressions of 15- and 5-lipoxygenases in leukocytes and the changes of the levels of blood lipoxin A4 (LXA4 ) and leukotriene C4 ( LTC4) in children with asthma. Methods The mRNA levels of 15- and 5-lipoxygenases in leukocytes were assessed by RT-PCR, and the levels of blood LXA4 and LTC4 were determined by ELISA, in 106 children with mild, moderate and severe asthma. Forty healthy children served as the controls. Results In children with mild, moderate and severe asthma, the relative mRNA levels of 15-lipoxygenase in leukocytes were 1.78 ±0.56, 1.28 ±0.45 and 0. 58 ±0. 22 (F = 16. 72, P <0. 01), respectively, and all were higher than that of the controls (0. 26 ± 0.12, P<0.05). The levels of blood LXA4 were (5.52±1.97), (1. 86 ±0.72) and (0. 81 ±0. 36) μg/L (F =22. 59, P <0.01), respectively, decreasing with the severity of asthma, and all were higher than that of the controls [ (0. 04 ±0. 01) μg/L, P <0. 05]. There was a positive correlation between PEF, FEV, and blood LXA4. The relative levels of 5-lipoxygenase mRNA in leukocytes were 0. 26 ±0. 12, 0. 79 ±0. 34 and 1. 21 ±0. 52,respectively in children with asthma of mild, moderate and severe degree(F = 18. 64, P <0. 01) ,which showed an increase with the severity of the disease, and all of which were higher than that of thecontrols (0.12 ±0.05, P< 0.05). The levels of blood LTC4 were (22.4 ± 8. 2 ), (54.6±28.4) and (118. 7 ±41. 1) ng/L ( F = 25. 91, P < 0.01), respectively, also showing an increase with the severity of asthma, and were higher than that of the controls [ (6. 8 ± 2. 5 ) ng/L, P < 0. 05 ]. There was a negative correlation between PEF, FEV, and blood LTC4. Conclusion The reversed changes of 15-lipoxygenase product LXA4 and 5-lipoxygenase product LTC4 in children with asthma of mild, moderate and severe degree suggests that insufficiency of LXA4, an physiological antagonist to leukotrienes, and an overproduction of LTC4 , may be involved in the pathogenesis of worsening of asthma in children.