The glycophoryn A (GPA) assay evaluates somatic in vivo mutations. It is considered a cumulative biodosimeter for genotoxic exposures and is under evaluation in cancer risk assessment.GPA, a polymorphic membrane protein of the erythrocytes, determines the MN blood groups. The N0 and NN variant frequencies (VF) may be detected in MN subjects (about 50% of the population) by flow cytometry using two differently labelled antibodies.We explored if GPA N0 and NN VF might be relevant to the assessment of individual lung cancer risk and susceptibility, in a small population with a high prevalence of heavy tobacco smokers: 8 lung cancer patients and 16 subjects with non‐malignant lung diseases associated with increased risk of lung cancer.There was a wide interindividual variability and complete overlap between non‐neoplastic and neoplastic patients. A significant positive correlation was seen with smoking duration in N0 VF (p=0.04, age‐adjusted). Current smokers (n=12) displayed higher N0 values than never (n=1) or ex‐smokers (n=11), 36.3±18.2 and 21.0±13.2, respectively (p < 0:01). No association was shown with occupational exposure.The present exploratory study suggests that assessment of individual lung cancer risk and susceptibility by the GPA assay does not seem to be feasible. The assay appears to provide a biomarker of longterm exposure to tobacco smoke.