Objectives: Hemoptysis is an alarming symptom of underlying lung disease. Clinicians are often unsure how to deal with and follow up patients who have had a single episode of hemoptysis, especially if the cause remains unknown despite thorough examination, because a second, more severe episode of hemoptysis might occur despite an apparently stable condition. Investigations were done, using multivariate analyses, to see whether several clinical factors present during an initial episode of hemoptysis could be used to predict a second episode. Subjects and Methods:Eighty patients with an initial episode of hemoptysis who underwent both computed tomographic and bronchoscopic examinations from 2003 through 2005 were reviewed. Results:The isolation of bacteria from bronchial lavage fl uid (odds ratio 13.5, P = 0.001) and the failure to determine the cause of the initial episode of hemoptysis (odds ratio 7.0, P = 0.014) were signifi cant independent predictors of a second episode of hemoptysis. Subset analysis showed that isolation of either Pseudomonas aeruginosa or Haemophilus infl uenzae increased the likelihood of a second episode of hemoptysis (P = 0.077), even if colonization, representing host-bacterial equilibrium, had occurred. Furthermore, the failure to determine the etiology of an initial episode of hemoptysis was associated with an increased risk of a massive second episode (P = 0.042), regardless of the volume of the initial episode. Conclusions:In patients with bacterial colonization of the respiratory tract or an initial episode of hemoptysis of unknown etiology, there is an increased possibility of a second episode of hemoptysis.