Hepcidin is a peptide that regulates iron homeostasis by inhibiting iron absorption by the small intestine and release of iron from macrophages. Its production is stimulated by iron overload and by inflammation. It has been suggested that IL-6 is the only cytokine that stimulates hepcidin transcription. However, mice with targeted disruption of the gene encoding IL-6 (IL-6-/-) respond to endotoxin by increasing the expression of hepcidin transcripts in the liver. We show that incubating murine hepatocytes with IL-6, IL-1alpha, and IL-1beta strongly stimulates hepcidin transcription. IL-10 has little or no stimulatory effect, and IFN-beta inhibits transcription of hepcidin. All of the hepcidin stimulatory activity of macrophages from IL-6-/- mice can be accounted for by IL-1 that they secrete. Hepatocytes from IL-6-/- mice, hfe-/- mice, and mice with a hypomorphic transferrin receptor 2 mutation responded to IL-6 and IL-1 by up-regulating hepcidin transcription. Nitric oxide does not seem to be involved in the stimulation of hepcidin transcription by cytokines: aminoguanidine does not inhibit the stimulation of hepcidin transcription by cytokines. IL-1 may play a significant role in the anemia of inflammation by up-regulating hepcidin.