Abstract: Methods and compositions are provided for detecting antigens having a specific epitope associated with squamous lung carcinoma. The antigen may be found at lesion sites or in the blood as indicative of the squamous lung carcinoma.Specific antibodies may be used for the detection of the antigen and in therapy.The mouse hybridoma 43-9F producing IgM monoclonal antibody 43-9F and SLC cell RH-SLC-L11 were deposited at The PHLS Centre for Applied Microbiology and Research, Porton Down, Salisbury, U.K. on Jan. 31, 1985 and given Accession Nos. 85013101 and 85061403, respectively.