The complete amino acid sequence of a potassium channel protein of rat brain, Kv3.2b, plus a partial sequence of a related channel, Kv3.2c, are deduced from molecular cloning of the respective cDNA's. Kv3.2b and Kv3.2c share extensive amino acid sequence identity with a previously identified channel, RKShIIIA[1], before diverging to unique carboxy termini. Probes specific for Kv3.2b and RKShIIIA detect similarly sized mRNA's on Northern blots. These two proteins are encoded by a single gene based on genomic Southern blotting, and therefore arise by alternative splicing. In vitro transcribed mRNA for Kv3.2b induces the expression of outward K+ currents in Xenopus oocytes under voltage-clamp conditions.