Fiberoptic bronchoscopy remains the gold standard to establish the presence or absence of acute pulmonary allograft rejection or infection after lung transplantation (LT). Performance of clinically mandated transbronchial lung biopsy enhances diagnostic precision and has 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 that can assist long-term management. Moreover, knowledge about the structural integrity of the bronchial anastomosis is critical to achieve optimum outcomes. Obliterative bronchiolitis (OB) is the most common cause of late graft dysfunction and mortality 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. The major risk factor for BOS is thought to be acute cellular rejection but new data support an important role for lymphocytic bronchiolitis. This review examines the role of fiberoptic bronchoscopy after LT as a surveillance tool and discusses indications, risk:benefit, and outcomes, with emphasis on two specific findings on biopsy; namely, minimal acute cellular rejection and lymphocytic bronchiolitis. Findings on follow-up biopsies to assess the outcome of therapies and the natural history of untreated "minimal" rejection events are also discussed.