Lung cancer patients have been reported to have generalized immune dysfunction of the cell-mediated immune response. In contrast, little is known about the humoral immune function in these patients. Therefore, we examined the IgG subclass distribution (IgG1-lgG4) in 67 lung cancer patients (23 adenocarcinoma, 29 squamous cell carcinoma, 15 small cell carcinoma), 13 patients with inflammatory lung diseases, seven patients with pulmonary metastasis and 23 healthy controls using a commercial available ELISA. We found a significant increase in the percentage of IgG1 in adenocarcinoma, compared with squamous cell and small cell lung carcinoma (P < 0.05). Small cell lung cancer patients showed an increase in IgG2, IgG3 and IgG4 compared with all other groups (P < 0.05, respectively). IgG1/lgG2, IgG1/lgG3 and IgG1/lgG4 ratios in adenocarcinoma were higher than in small cell lung cancer (P < 0.05). In the squamous cell carcinoma there was no difference in IgG subclass distribution compared to controls. Our study demonstrates that the different histological subtypes of lung carcinoma influence the IgG subclass distribution. Whether this phenomenon is the result of a direct influence on B-cell activity by the tumor needs further investigation.