An early event during inflammation and infection is the migration of monocytes into tissues where they differentiate into macrophages. Such monocyte-derived macrophages face an unfavorable environment characterized by extremely low oxygen tension and accumulation of reactive oxygen species such as hydrogen peroxide. Previous experiments showed that a macrophage cell line cultured under these conditions responded to inflammatory stimulants with an increased respiratory burst compared to cells kept at regular ambient oxygen conditions. The objective of the present study was to test if this effect was accompanied by an increased cytokine production. Using cytokine protein arrays and real time gene expression analysis, we indeed found that low oxygen exposure increased expression of characteristic macrophage inflammatory cytokines such as IL-1, IL-6, and TNF-alpha. Interestingly, cells exposed to low oxygen and steady-state hydrogen peroxide levels did not show this increase, indicating different cell mechanisms might be involved in increasing macrophage hydrogen peroxide and cytokine release.