Objective. To investigate the roles of apoptosis in the pulmonary artery remodeling of pulmonary hypertension secondary to hypoxia and illustrate the relative genes expression. Methods. Thirty rats were divided into hypoxia group（ 10％ O2

8h/d） and normal control group. On the 15th day of hypoxia

pulmonary artery pressure and right ventricular hypertrophy index were measured and pulmonary artery vessels were studied by light microscope. Then terminal deoxynucleotidyl transferase- mediated dUTP nick- end labeling（ TUNEL） technique was used to detect nucleosomal DNA fragmentation of apoptotic cells. In situ hybridization and RT- PCR were used to detect the expression level of bcl- 2 and bax. Results. The pulmonary artery pressure and right ventricular hypertrophy index of hypoxia group were increased significantly

the pulmonary artery wall of hypoxic group become incrassate than control group. Apoptotic cells can be found in lung with hypoxia or without hypoxia. Compared with control group

apoptotic index of hypoxic group decreased significantly. Through the methods of in situ hybridization and RT- PCR

we found the expression of bcl- 2 increased whereas bax decreased significantly in the hypoxic group. Conclusion. The alternation in bcl- 2 and bax expression induced by hypoxia play an important role in the pulmonary artery remodeling which is the main pathologic change of pulmonary hypertension secondary to hypoxia.