BACKGROUND: Bronchofiberscopy is a procedure with a chance of airway irritation and it may cause pathophysiologic changes of respiratory system. So we tried to evaluate the influence of bronchofibercopy on O2 saturation, ABGA and PET by patient's basal status and procedure type. METHOD: O2 saturation was measured every 1 minute from the left index finger tip with percutaneous oximetry. ABGA was done before and right after the bronchofiberscopy and PFT was done before and within 10 minutes after the bronchofiberscopy. RESULTS: The mean time for bronehofiberscopy procedure was 14.5mim and SaO2 maximally fall to 89.0 below 8% of the baseline after mean time of 8.4mm, which was recorvered at the end of the procedure. SaO2 change amount was 8.4% on Non-O2 supply group, which was lower compared to 6.4% of the O2-supply group without statistically significance. Biopsy Group and BAL group showed more SaO2 fall than washing only group. The level of PaO2 and FEV1 of the patient didn's influence significantly on SaO2 fall during the procedure. ABGA taken before and after the bronchofiberscopy showed mild fall of Pa02 and mild rise of PaCO2. Whereas PET showed decrease of FEV1(P<0.05) and increase of RV without changes in airway resistance and pulmonary diffusion capacity. Comparing before and after the bronchofiberscopy, the washing group showed no significant changes on PET, while the biopsy group and the BAL group showed increase of RV & decrease of FEV1 after the bronchofiberscopy. BAL group showed more changing tendency rather than biopsy group although not statistically significant. CONCLUSION: Bronchofiberscopy is considered as a relatively safe procedure, but it would be better to be done with O2 supply especially in the patient with low PaO2 and in the case of biopsy and BAL.