Objective To investigate the role of transbronchial lung biopsy ( TBLB) in the diagnosis and prognosis evaluation of idiopathic interstitial pneumonia ( IIP) . Methods Clinical data of IIP patients admitted to Peking University First Hospital from January 2005 to April 2009 were analyzed retrospectively. The pathologic manifestations of TBLB samples of these patients had been reviewed by pathologists and respirologists. Chest high-resolution computer tomography ( HRCT) of the patients had been reviewed, and subsequent follow-ups were performed. The influence factors on diagnosis value of TBLB were analyzed. The relationship between TBLB findings and prognosis were observed. Results 29 IIP patients had been investigated, among them 21 were male and 8 were female, ranging in age from 43 to 79 years, with an average of 63 ±10 years.16 TBLB samples had diagnostic value, among themthe total number of the samples was from 2 to 7, with an average of 4.2 ±1.8. 13 TBLB samples had no diagnostic value, among them the total number of the samples was from0 to 5, with an average of 2.1 ±1.6. There was significant differences between two groups( P lt;0.005) . Among the 16 cases with diagnostic value of TBLB, non-specific interstitial pneumonia ( NSIP) pattern was showed in 9 cases, usual interstitial pneumonia ( UIP) pattern in 6 cases and organizing pneumonia ( OP) in 1 case. Among 29 cases, UIP-like pattern was showed on HRCT in 14 cases, while non-UIP pattern showed on HRCT in 15 cases. On follow-up of the 16 patients, 1 patient aggravated and 5 patients died among 6 cases with UIP pattern, 8 patients got better and 1 patient died among 9 cases with NSIP pattern, and the patient with OP got better. The patients who show non-UIP pattern in TBLB survived longer than UIP pattern with significant difference between two groups ( P lt; 0.005) . Conclusions The diagnosis value of TBLB is bly related to the number of samples and the patterns of HRCT. When the number of samples is more than or equal to 3, the diagnosis value of TBLB is better. It is easier to get valuable TBLB samples in patients with non-UIP pattern on HRCT than that with UIP pattern. The patients with non-UIP pattern in TBLB have better prognosis than those with UIP pattern. TBLB is useful in diagnosis and prognosis evaluation of IIP.