Objective To evaluate the safety and diagnostic yield of transbronchial lung biopsy ( TBLB) performed in mechanically ventilated patients. Methods TBLB was performed in 19 mechanically ventilated patients form January 2001 to September 2007 in the ICU of Guangzhou Institute of Respiratory Diseases. The results of clinical data were retrospectively analyzed. Results A total of 19 patients were analyzed[ 9 female, 10 male, with amean age of ( 57. 94 ±15. 00) years] . Specific diagnoses were made in 9 cases ( 47. 4% ) by TBLB. The diseases included pulmonary aspergillus pneumonia in 4 cases ( 21. 0% ) ,lung cancer in 2 cases ( 10. 5% ) , radioactive pneumonia in 1 case( 5. 3% ) , Goodpasture’s syndrome in1case( 5. 3% ) , pulmonary tuberculosis in 1 case ( 5. 3% ) . Ten cases ( 52. 6% ) were not able to establish confirmed diagnoses including pulmonary interstitial fibrosis in 6 cases( 31. 6% ) and lung tissue nonspecific changes in 4 cases( 21. 0% ) . The treatment was adjusted according to the results of TBLB in 10 patients( 52. 6% ) . Complications associated with this procedure included episodes of bronchial hemorrhage of ≥30 mL in 4 cases ( 21. 0% ) , transient oxygen desaturation in 11 cases ( 57. 9% ) , hypotension in 5 cases ( 26. 3% ) , and transient tachycardia in 1 case ( 5. 3% ) without death and pneumothorax. Conclusions TBLB can be performed safely and has a diagnostic value in mechanically ventilated patients. TBLB should be considered as a diagnostic procedure before open lung biopsy.