The Elk subfamily of the Eag K+ channel gene family is represented in mammals by three genes that are highly conserved between humans and rodents. Here we report the distribution and functional properties of a member of the human Elk K+ channel gene family, KCNH8. Quantitative RT-PCR analysis of mRNA expression patterns showed that KCNH8, along with the other Elk family genes, KCNH3 and KCNH4, are primarily expressed in the human nervous system. KCNH8 was expressed at high levels, and the distribution showed substantial overlap with KCNH3. In Xenopus oocytes, KCNH8 gives rise to slowly activating, voltage-dependent K+ currents that open at hyperpolarized potentials (half-maximal activation at -62 mV). Coexpression of KCNH8 with dominant-negative KCNH8, KCNH3, and KCNH4 subunits led to suppression of the KCNH8 currents, suggesting that Elk channels can form heteromultimers. Similar experiments imply that KCNH8 subunits are not able to form heteromultimers with Eag, Erg, or Kv family K+ channels.