Abstract: Objective : We measured the concentration of CYFRA21-1 and cancer cells in Bronchoalveolar Lavage Fluid (BALF) and serum to evaluate the diagnostic value in lung cancer. Methods : CYFRA21-1 levels were measured with Immunoradiometricassay (IRMA) in the BALF and serum. The diagnostic value of this method in lung cancer was compared with fiberoptic bronchoscopic biopsy and brushing. Results : 1) The levels of CYFRA21-1 in BALF and serum for patients with lung cancer was significant higher than that in benign pulmonary disease patients (B<0.05, P <0.01). 2)CYFRA21-1 in BALF, the sensitivity(75.0%) and accuracy (83.3Y) of Stages I and II in BALF were significant higher than that in serum (6.3% , 50.0Y) (P <0.01, P <0.05). 3) The positive rate for CYFRA21-1 and cancer cells in BALF of peripheral lung cancer was 77.3% and 72.7%, significantly higher than that of biopsy (9.1%) or brushing (36.4%) (P<0.05). Conclusions : BALF was more ideal biologic medium than serum for diagnosing lung cancer in the early stagesI The positive rate for CYFRA21-1 and cancer cells in BALF of peripheral lung cancer was significantly higher than that of biopsy or brushingI This may be a valuable adjunctive method in the diagnosis for peripheral lung cancerI