This study was conducted to explore the changes of PC III (type III procollagen) and C IV (type IV collagen) in the serum in patients with chronic pulmonary heart diseases. The blood levels of PC III and C IV in 25 patients with chronic pulmonary heart diseases and 20 normal subjects were measured by radioimmunoassay and were analysed in relation with the artery blood gas and pulmonary function parameters. The results revealed that the blood levels of PC III and C IV in the patients were significantly higher than those in normal subjects, and were negatively correlated with PaO2, FEV1%, MBC and MMEF (P < 0.05, P < 0.01). The results suggest that the blood levels of PC III and C IV of patients with chronic pulmonary heart diseases are significantly increased and significantly correlated with pulmonary function damage and hypoxia.