ObjectiveTo investigate the characteristics of nosocomial infection (NI) in patients with lung cancer treated by chemotherapy. MethodsA retrospective analysis on clinical data of 2 067 patients with lung cancer from January, 2003 to December ,2007 was made. ResultsThe NI rate in patients with lung cancer treated by chemotherapy was 7.93%. Upper respiratory tract infection and  lower respiratory tract infection was 51.11% and 33.89% respectively. Patients’ characteristics, including average hospital stay, average chemotherapy cycles, the degree of leukopenia and application of granulocyte colony stimulating factors were not obviously different between patients  with  and without NI (all P>0.05). NI rate increased significantly in patients with grade Ⅲ or Ⅳ leukopenia (P=0.000), but there was no difference in NI rate between patients receiving and not receiving preventive antimicrobial agents (both P>0.05).ConclusionThe most common NI in patients with lung cancer during chemotherapy are upper respiratory tract infection and   lower respiratory tract infection. Taking antimicrobial agents as a preventive measure against infection seems to have no effect on decreasing  NI rate in patients with grade Ⅲ or Ⅳ leukopenia.