To investigate the mRNA expression of Clara cell secretory protein (CCSP) and the Clara cell number in airways of rat asthma remodel.A rat asthma model was established by sensitization and challenge with ovalbumin (OA). The mRNA expression of CCSP in the lung tissue, the CCSP level in bronchial alveolar lavage fluid (BALF), the thickness of the airways and the number of Clara cells in bronchioles were determined by RT-PCR, image analysis system, dot immunoblotting and immunohistochemistry methods.There was a progressive decline in CCSP mRNA expression in the lung tissue of rat asthma model group (0.53 +/- 0.07 and 0.49 +/- 0.03, respectively, after 1 week and 2 weeks of challenge) as compared to that of control group (0.67 +/- 0.04). The CCSP levels in BALF of asthma model group (47.00 +/- 6.58 and 45.95 +/- 3.20, respectively, after 1 week and 2 weeks of challenge) were significantly decreased than that of control group (63.08 +/- 2.84, P < 0.01). The ratio(%) of Clara cells was also reduced after challenge. The WAt/Pbm, WAi/Pbm, and WAm/Pbm were significantly increased 2 weeks after OA challenge and were negatively correlated with the level of CCSP and its mRNA expression.The Clara cells and CCSP may participate in the pathogenesis of asthma in the rat asthma remodel.