In contrast to our understanding of molecular chaperones that help the folding of globular proteins,information on chaperones for fibrous proteins such as collagen has been limited.We have studied the structure and function of the ER-resident protein Hsp47,which functions as a chaperone specific for collagen.We have shown that,in vitro,Hsp47 inhibits fibril formation by collagen (1).This activity of Hsp47 is now regarded as its likely function in vivo,where it could prevent premature intracelluar aggregation of triple-helical procollagen in the ER.We have also identified Hsp47 binding regions in collagen using CNBr peptides derived from collagen (2).Recently,we have screened a chemical library and identified several small-molecular weight inhibitors that effectively inhibit Hsp47 by preventing its action on collagen (3).These inhibitors have therapeutic potential in diseases where collagen is excessively produced.Our recent data gathered from cell culture andmouse model studies indicate the potential for some of these inhibitors to arrest tumour growth.