To investigate the relationship between plasma levels of TXB2, 6-KPGF1?, cAMP and cGMP and the hemodynamics of hypoxemia, 30 patients with chronic cor pulmonale (CCP) were studied. The influence of hypoxemia and isosorbide dinitrate therapy was also observed. The results showed: 1) Plasma TXB2 level was significantly higher and plasma 6- KPGF1? level was significantly lower in CCP patients than in healthy controls. There was a negative correlation between 6 KPGFl? and-Ppa levels and a positive correlation between TXB2, TXB2/ 6 KPGF1? ratio and Ppa levels. 2) High levels of plasma TXB2 and TXB2 / 6-KPGF1? were found in hypoxemia cases when the PaO2 level was less than 6.67 kPa (50 mmHg). 3) Reduced Ppa after isosorbide dinitrate infusion elevated the plasma levels of 6-KPGF1?, cAMP, and the cAMP/cGMP ratio, and reduced those of TXB2 and the TXB2/6-K.PGF1? ratio.