There is no single cell type present in bronchoalveolar lavage (BAL) fluid that appears to be predictive for sarcoidosis. However, BAL fluid analysis can be very helpful in the differential diagnosis. A grouping of features, an elevated total cell count, predominantly lymphocytes, together with a nearly normal percentage of eosinophils and polymorphonuclear neutrophils and the absence of plasma cells, distinguish the most likely diagnosis of sarcoidosis from the most common interstitial lung diseases, extrinsic allergic alveolitis (EAA), nonspecific interstitial pneumonia (NSIP), and idiopathic pulmonary fibrosis (IPF). In sarcoidosis the majority of cases have an increased number of lymphocytes and a normal amount of eosinophils and neutrophils. Disease presentation or activity at the time the BAL is performed as well as the smoking status is crucial for interpretation of individual BAL fluid analysis results. In severe cases the number of neutrophils can be increased as well. For an individual case the CD4:CD8 ratio is of less importance because it can be increased, normal, and even decreased. In the follow-up depicting prognosis and response to treatment, BAL fluid analysis has less clinical relevance.