The evidence concerning open lung biopsy (OLB) for diffuse pulmonary infiltrates in patients with AIDS is limited. This study retrospectively evaluated the diagnostic and therapeutic yields of OLB compared with bronchoscopy for patients with AIDS with diffuse pulmonary infiltrate treated in the National Taiwan University Hospital from 1997 to 2004. There were 15 and 46 patients enrolled in the OLB and bronchoscopic groups in this study, respectively. As compared with the bronchoscopic group, patients from the OLB group had a higher chance of acquiring a specific diagnosis and possible change of therapy (73 vs 32.6% and 60 vs 21.7%, respectively; P < 0.05). There were two (13.3%) patients with prolonged air leak (greater than 7 days) in the OLB group, whereas four patients (8.7%) had procedure-related complications in the bronchoscopic group. There was no procedure-related mortality in the OLB group. This study demonstrated that OLB can be safely performed in select patients and provide a superior diagnostic and therapeutic benefit compared with bronchoscopy for diffuse pulmonary infiltrates in patients with AIDS. This procedure should be performed early in the clinical course to avoid irreversible clinical deterioration of the patients with severe illness.