Visfatin is a novel adipocytokine exerting insulin-mimetic effects in various insulin-sensitive tissues such as liver, muscle, and fat. In contrast, interleukin (IL)-6 is a proinflammatory adipose-secreted factor that induces insulin resistance and plasma concentrations that correlate with the development of type 2 diabetes mellitus. In the present study, the impact of IL-6 on visfatin gene expression in 3T3-L1 adipocytes was determined by quantitative real-time reverse transcription-polymerase chain reaction. Interestingly, 30 ng/ml IL-6 time-dependently downregulated visfatin synthesis with a significant 40% suppression seen after 4 h of treatment. Furthermore, the addition of IL-6 for 16 h dose-dependently suppressed visfatin mRNA with significant effects first observed at concentrations as low as 3 ng/ml and a maximal 43% reduction at 30 ng/ml effector. Moreover, inhibitor studies suggested that the negative effect of IL-6 on visfatin expression is, at least in part, mediated by p44/42 mitogen-activated protein kinase. In contrast, troglitazone did not reverse the negative effect of IL-6 on visfatin synthesis under these conditions. Taken together, our study suggests that IL-6 might influence glucose tolerance in part by regulation of the novel insulin-mimetic adipocytokine visfatin.