BACKGROUND: Open lung biopsy(OLB) has conventionally been regarded as the gold standard for the diagnosis in interstitial lung disease. With recent advances in diagnostic technique such as high resolution computed tomography(HRCT), and transbronchial lung biopsy(TBLB) which provide relatively accurate diagnosis of ILD, it is necessary to reevaluate the role of these methods in the diagnosis of ILD. METHODS: We carried out a retrospective analysis of nineteen patients who underwent OLB at Dankook University Hospital for the diagnosis of acute and chronic ILD, between May 1995 and June 1998. By reviewing the medical records, the demographic findings, underlying conditions, HRCT and TBLB findings, OLB diagnosis, therapy after OLB, and complication of OLB were evaluated. RESULTS: 1) Thirteen patients(68.4%) had chronic ILD(symptom duration over 2 weeks prior to OLB), and six patients(31.6%) had acute ILD(symptom duration less than 2 weeks). 2) Specific diagnosis were reached in 92%(12/13) of chronic ILD(5 Bronchiolitis obliterans organizing pneumonia(BOOP), 2 constrictive bronchiolitis, 3 Usual interstitial pneumonia, 1 hypersensitivity pneumonitis, 1 eosinophilic pneumonia), and in all patients of acute ILD(5 acute interstitial pneumonia, 1 pneumocystis carinii pneumonia). 3) HRCT were performed in all patients and a correct first choice diagnosis rate of HRCT was 42%(5/12) in chronic ILD. 4) In chronic ILD patients, 62%(8/13) received specific therapy(steroid therapy in 7 patients and moving in one patient), after OLB, but in acute ILD, all patients received specific therapy(steroid therapy in 5 patients and steroid and antibiotic therapy in one patient) after OLB. 5) The in-hospital mortality after OLB was 5.3%(1/19). CONCLUSION: OLB is an excellent diagnostic technique with relatively low complications in patients with ILD. Therefore OLB should be considered in patients with ILD when the specific diagnosis is important for the treatment, especially in patients with acute ILD.