The purpose of this study was to examine the role of the plasminogen system in the development of adipose tissue. Plasminogen binding capacity was determined in differentiated and undifferentiated cells from adipose tissue of plasminogen deficient mice and 3T3 cells, a well-characterized tissue culture model. In 3T3 cells, plasminogen binding was fivefold higher in differentiated cells compared to the undifferentiated cells. Inhibition of binding by carboxyl-terminal lysine analogs was similar for the differentiated and undifferentiated cells with tranexamic acid > EACA > lysine. The binding of plasminogen was concentration-dependent and approaches saturation in the both cell types. The number of plasminogen binding sites was tenfold higher in the differentiated compared to the undifferentiated cells. In isolated mature fat cells and stromal cell cultures from mouse adipose tissue, plasminogen binding was also higher in the differentiated mature fat cells and differentiated stromal cells compared to undifferentiated stromal cells. Plasminogen binding was elevated in the differentiated cells from the Plg-/- mice compared to cells from the WT mice. These results suggest that the plasminogen system plays an important role in adipose tissue development.