The avian and mammalian tectorial membranes both contain two non-collagenous glycoproteins, a- and ß-tectorin. To determine whether variations in the primary sequence of the chick and mouse a-tectorins account for differences in subunit composition and matrix structure of the tectorial membranes in these two species, the cDNA for chick atectorin was cloned and sequenced. The derived amino acid sequence was found to have 73% identity with mouse a-tectorin, suggesting that the tectorins are highly conserved proteins. The central region of chick a-tectorin contains fewer potential N-glycosylation sites than that of mouse a-tectorin and is cleaved at two additional sites. The extra glycosylation sites in the mouse sequence may help occlude sites of proteolytic attack. In situ hybridisation and northern blot analysis indicate that the spatial and temporal patterns of chick a- and ß-tectorin mRNA expression in the inner ear are different, suggesting that the two tectorins may each form homomeric filaments. Early functional recovery in the chicken after sound damage has been attributed to the rapid regeneration of the tectorial membrane. In situ hybridisation indicates that both aand ß-tectorin mRNAs are upregulated in the sound damaged basilar papilla. The regenerated tectorial membrane contains both a and ß-tectorin proteins. In order to understand how the tectorin genes are regulated during development and regeneration, the upstream non-coding region of the ß-tectorin genes from mouse and chicken were compared in an attempt to identify potential regulatory elements. DNA sequence alignments of the chick and mouse ß-tectorin upstream sequence show low identity, suggesting that the chick and mouse ß-tectorin promoters have not remained functionally conserved throughout evolution.