Interleukin (IL)‐11 is a member of the gp130 family of cytokines. Comparison of IL‐11 with another gp130 family member, IL‐6, indicates that these two cytokines share many overlapping signal transduction mechanisms. However, unlike IL‐6, treatment of patients with a recombinant human form of IL‐11 (rhIL‐11) does not increase body temperature, suggesting significant differences in the in vivo function of these two molecules. Recent studies demonstrate that IL‐11 has potent anti‐inflammatory activity in a variety of preclinical animal models of disease. rhIL‐11 reduces production of proinflammatory mediators such as tumor necrosis factor‐α and IL‐12 from activated macrophages. This effect on proinflammatory cytokine production is mediated at the transcriptional level by inhibition of the transcription factor, NF‐ΚB. To further understand the anti‐inflammatory mechanisms of action of rhIL‐11 and to elucidate differences between IL‐11 and IL‐6 signal transduction pathways, the effects of these two cytokines on in vitro macrophage function were compared.