Leptin is a hormone secreted by adipocytes. Besides controlling appetite and body weight, it has been suggested that leptin plays a role in inflammation and hemopoiesis. In this study we demonstrate that the pro-inflammatory/hemopoietic cytokines, IL-1beta, IL-6, TNF-alpha, and interferon-gamma, significantly inhibit gene expression and secretion of leptin by bone marrow adipocytes. These findings are in agreement with the data recently obtained from non-medullary adipose tissues. Within the bone marrow environment, leptin regulation by these pleiotropic cytokines could contribute to controlling the proliferation and differentiation of hemopoietic precursors as well as the maturation of stromal cells.