Objective To investigate the relations between the human beta defensin-2 (HBD-2) and systemic inflammatory responses in patients with lower respiratory tract infection（LRTI）. Methods Eighty-one patients with confirmed LRTI including community-acquired pneumonia，acute exacerbation of chronic obstructive pulmonary disease or concurrent lung infection，and bronchiectasis concurrent infection were enrolled，and twenty healthy volunteers were included as control. Plasma concentrations of HBD-2，IL-1β，and IL-8 were assayed with ELISA method in all patients and controls. Furthermore the patients were divided into three groups according to the onset of disease:,ie.group A （shorter than 7 days），group B （7 to 14 days），and group C （more than 14 days）. The differences between these groups were compared. Correlation between HBD-2 and IL-1β or IL-8 concentrations was analyzed. Results HBD-2，IL-1β，white blood cell （WBC） of the peripheral blood in the patients with LRTI were all significantly higher than those in the healthy controls. HBD-2 and IL-1β increased in group A and group B，and decreased in group C comparing to the control group （Plt;0.05 respectively）. There was no significant difference of IL-8 in group A，B and C. HBD-2 showed a positive linear correlation with IL-1β （r=0.313，P=0.030） and no correlation with IL-8（Pgt;0.05）. Conclusions The plasma HBD-2 concentration is increased in LRTI patients，which may be a biomarker of systemic inflammation in the early or relative early course of LRTI.