It is known that the anemias of chronic diseases, which often occur in neoplastic and in systemic inflammatory disorders, are characterized by high levels of ferritin associated with generally low iron concentrations, by suggesting an iron transfer defect due to unknown factors. Since both chronic inflammatory diseases and advanced neoplasms are characterized by alterations in the endogenous production of cytokines, a possible involvement of interleukins in chronic disease-related anomalies of iron metabolism cannot at present be excluded. The present study was carried out to investigate the effect of low-dose IL-2 subcutaneous immunotherapy (3 million IU/day for 6 days/week for 4 weeks) on ferritin, transferring and iron serum levels in cancer patients. Six patients with metastatic gastrointestinal carcinomas were evaluated. Ferritin mean levels significantly decreased during IL-2 treatment, and this finding was associated with a significant increase in transferrin values. Iron mean levels increased in response to IL-2, without, however, significant differences in respect to the pretreatment concentrations. These preliminary data, by showing changes in ferritin, transferrin and iron in cancer patients during the immunotherapy with IL-2, would suggest the existence of a cytokine regulation of iron transfer from tissues to blood, perhaps by modulating the macrophage function.