We have cloned from the receptor epithelium of the chick cochlea a family of alternatively spliced cDNAs derived from cslo, which encodes a Ca2+-activated K+ channel like those shown to help determine the resonant frequency of electrically tuned hair cells. Our results from PCRs using template RNAs from both tonotopically subdivided receptor epithelia and single hair cells demonstrate differential exon usage along the frequency axis of the epithelium at multiple splice sites in cslo. We also show that single hair cells express more than one splice variant at a given splice site. Since channel isoforms encoded by differentially spliced slo transcripts in other species are functionally heterogeneous, these data suggest that differential processing of slo transcripts may account, at least in part, for the systematic variation in hair-cell membrane properties along the frequency axis of electrically tuned auditory receptor epithelia.