The concentrations of total serum IgA and IgG of 267 patients with different primary malignant tumors were measured by ELISA. Total serum IgA increased by 30% to 40% in patients with malignancies associated with mucous membranes (nasopharyngeal, gastrointestinal and bronchial carcinomas), while the change in total serum IgG was negligible. Although, the changes in Ig level could be influenced by many host factors, these data call attention to the potential indicative role of total serum IgA levels. Further studies are required to establish links between serum IgA levels and stages of tumor growth or tumor progression in order to use these values as prognostic factors.