Despite advances in gene and immunological monitoring techniques that hold great promise for the future, fiberoptic bronchoscopy remains the gold standard to establish the presence or absence of acute pulmonary allograft rejection or infection after lung transplantation (LT). There is general agreement that clinically mandated transbronchial lung biopsies enhance diagnostic precision and have a satisfactory risk:benefit ratio in experienced hands. Surveillance transbronchial biopsies have a lower yield but may provide longitudinal insight into immunological events in the allograft, which can assist long-term management. Indeed, much of our knowledge about the significance of allograft histopathological events over time has been garnered from centers that perform routine surveillance procedures, and it is exactly the balance between individual and community benefit which underscores discussion about the value of invasive monitoring. Obliterative bronchiolitis (OB) is the most common cause of late chronic allograft dysfunction leading to death after LT. Significant OB is invariably associated with reduced graft function, denoted physiologically by the bronchiolitis obliterans syndrome (BOS). Importantly, not all BOS is due to OB; hence the move to develop an all embracing phraseology for late graft dysfunction, specifically "chronic lung allograft dysfunction" (CLAD). The major risk factor for BOS was once thought to be acute cellular rejection (ACR), but new data support an important role for lymphocytic bronchiolitis (LB) independent of so-called vascular acute rejection, albeit when diagnosed and treated. This review examines the role of fiberoptic bronchoscopy after LT as a surveillance tool versus a clinically mandated diagnostic procedure.