Galectin-3 is a member of a growing family of beta-galactoside-binding animal lectins and previously designated as epsilon BP (IgE-binding protein) by this laboratory and as Mac-2, CBP35, L-34 and L-29 by other researchers. While possible intracellular functions have been proposed for galectin-3, existing data also suggest an extracellular modulatory role of this lectin. For example, epsilon BP/Mac-2 was found to be secreted by various cells and capable of activating mast cells, possibly through cross-linking of cell surface glycoproteins involved in cell activation. In this study, we showed that epsilon BP bound to human monocytes via its lectin function. Furthermore, we found that epsilon BP potentiated IL-1 production by monocytes in a manner that was inhibitable by the saccharide ligand of epsilon BP. The results further support a role of this lectin in potentiating activities of inflammatory cells and thereby amplifying inflammatory responses.