Background: Coronavirus disease 2019 (COVID-19) is an infectious respiratory disease caused by novel coronavirus SARS-CoV-2 predominately involving the respiratory system. Bronchoalveolar lavage (BAL) is a safe, easily performed, minimally invasive and well tolerated procedure which explores large areas of the alveolar compartment providing cells as well as non-cellular constituents from the lower respiratory tract. It opens a window to the lung.Alterations in BAL fluid cellular and non-cellular components reflect pathological changes in the lung parenchyma. The information obtained from BAL fluid analysis, if considered carefully can have a reliable diagnostic criterion.