We investigated 801 patients with lung infiltrates who underwent transbronchial lung biopsy (TBB) and performed cytologic studies of lavage fluid of 491 patients who also underwent bronchoalveolar lavage (BAL). A specific histopathological diagnosis was made in 232 cases (29%). Histopathological changes consistent with the clinical pattern were present in 296 cases (37%). The diagnostic yield of TBB was 66%. Routine evaluation of BAL fluid allowed us to make a specific diagnosis in 49 cases. The role of the pulmonary pathologist in the interpretation of TBB and BAL specimens is discussed.