Pancreatic secretory trypsin inhibitor from human pancreatic juice bound specifically to cultured cells derived from a variety of human and nonhuman tissues. The binding pattern of pancreatic secretory trypsin inhibitor to various cells was quite different from that of epidermal growth factor, and these two polypeptides did not compete in binding to cultured cells with one another, indicating that the binding site for pancreatic secretory trypsin inhibitor was distinct from the receptor for epidermal growth factor.