We have been interested in elucidating how simultaneous stimuli modulate inflammation-related signal transduction pathways in lung parenchymal cells. We previously demonstrated that exposing respiratory epithelial cells to 95% oxygen (hyperoxia) synergistically increased tumor necrosis factor- (TNF)-mediated activation of NF-B and NF-B-dependent gene expression by a mechanism involving increased activation of IB kinase (IKK). Since the signal transduction mechanisms induced by interleukin-1 (IL-1) are distinct to that of TNF, herein we sought to determine if hyperoxia modulates IL-1-dependent signal transduction. In A549 cells, simultaneous treatment with hyperoxia and IL-1 caused increased activation of IKK, prolonged the degradation of IB, and prolonged the nuclear translocation and DNA binding of NF-B compared to cells treated with IL-1 alone in room air. Hyperoxia did not affect IL-1-dependent degradation of the interleukin receptor associated kinase differently than treatment with IL- alone. In contrast to the effects on the IKK/IB/NF-B pathway, simultaneous treatment with hyperoxia and IL-1 did not augment NF-B-dependent gene expression compared to treatment with IL-1 alone. Similar observations were made in a different human respiratory epithelial cell line, BEAS-2B cells. In addition, simultaneous treatment with hyperoxia and IL-1 caused hyperphosphorlyation of the NF-B p65 subunit compared to treatment with IL-1 alone. In summary, concomitant treatment of A549 cells with hyperoxia and IL-1 augments activation of IKK, prolongs degradation of IB, and prolongs nuclear translocation and DNA binding of NF-B. This activation, however, is not coupled to increased expression of NF-B-dependent genes and the mechanism of this decoupling is not related to decreased phosphorylation of p65