Broncho-alveolar lavage is an important diagnostic instrument in lung transplantation. It can give insight into the mechanisms of acute and chronic rejection, but can also be of interest to explore the possible effects of new therapies. This has particularly been the case with azithromycin as add-on therapy for chronic rejection.Furthermore BAL after lung transplantation is important to differentiate between infection and rejection and the changes in the cellular profile may be of prognostic significance. Key-words: Broncho-alveolar lavage, lung transplantation, neutrophils