Studies in itro suggest that the C-terminus of tropoelastin mediates elastin polymerization through an interaction with microfibril-associated proteins. In this study we have used cultured auricular chondrocytes as a model system to examine whether this interaction is critical for elastic fibre formation in i o. Auricular chondrocytes, which deposit an abundant elastic fibre matrix, were cultured in the presence of Fab fragments of antibodies directed against the C-terminus (CT e ) or an N-terminal domain (AT e ) of tropoelastin. Immunofluorescent staining of the extracellular matrix deposited by the cells showed that the CT e antibody inhibited the deposition of elastin without affecting microfibril structure. Cells grown under identical conditions in the presence of AT e , however, formed fibres that stained normally for both elastin and microfibril proteins. Chondrocytes cultured in the presence of microfibril-associated glycoprotein (MAGP) : 21-35, an antibody directed against a domain near the