We report the isolation of a novel mouse voltage-gated Shaker-related K+ channel gene, Kv1.7 (Kcna7/KCNA7). Unlike other known Kv1 family genes that have intronless coding regions, the protein-coding region of Kv1.7 is interrupted by a 1.9-kilobase pair intron. The Kv1.7 gene and the related Kv3.3 (Kcnc3/KCNC3) gene map to mouse chromosome 7 and human chromosome 19q13.3, a region that has been suggested to contain a diabetic susceptibility locus. The mouse Kv1.7 channel is voltage-dependent and rapidly inactivating, exhibits cumulative inactivation, and has a single channel conductance of 21 pS. It is potently blocked by noxiustoxin and stichodactylatoxin, and is insensitive to tetraethylammonium, kaliotoxin, and charybdotoxin. Northern blot analysis reveals approximately 3-kilobase pair Kv1.7 transcripts in mouse heart and skeletal muscle. In situ hybridization demonstrates the presence of Kv1.7 in mouse pancreatic islet cells. Kv1.7 was also isolated from mouse brain and hamster insulinoma cells by polymerase chain reaction.