The standard armamentarium of tests that are used by pulmonologist are laboratory tests, pulmonary function tests, different radiological techniques (conventional chest-X rays, HRCT scans, etc) and pathohistological analyses of biopsies. The minimally invasive bronchoalveolar lavage (BAL) procedure, in addition to methods earlier mentioned, is an important diagnostic instrument that can facilitate the diagnosis of various diffuse lung diseases (DLD). BAL fluid white blood cell profiles are analyzed, malignant cells looked for, and in certain circumstances particular stains are performed to detect yet other cell types. Additionally, BAL can play a very important role in the diagnosis of respiratory tract infections. All these analyses are usually readily performed in a moderately equipped cytological laboratory.