Objective To evaluate the effects of indoor temperature and relative humidity on acute exacerbations of chronic obstructive pulmonary disease（AECOPD）.Methods A total of 70 moderate to very severe COPD patients were recruited.The data including indoor temperature and relative humidity twice daily，increase over their stable symptoms in "major" symptoms（dyspnea，sputum purulence，sputum amount） and "minor" symptoms（nasal discharge/congestion，sore throat，cough），and adjustment of medication were recorded on diary cards.All data were collected from Jan 2005 to Dec 2005 by telephone inquiring or home visiting.Furthermore，the corresponding median outdoor temperature，relative humidity and air pressure from atmosphere bureau were compared with indoors parameters to examine the different effects on AECOPD.Results Fifty-five cases completed the whole investigation.Indoor temperature and relative humidity were both risk factors when logistic regression was used to evaluate the effect.Our research showed that AECOPD was significantly related to indoor and ourdoor environment factors.The correlation coefficient of all factors were r=－0.686（indoor temperature），r=－0.671（outer temperature），r=0.105（indoor humidity），r=－0.115（outer humidity），r=0.545（atmospheric pressure） respectively.Conclusions The indoor temperature and relative humidity，especially low temperature and high relative humidity，had important effects on AECOPD of moderate to very severe patients.It may be helpful to prevent AECOPD by adjusting the indoor temperature and relative humidity.