The Shaw-type K+ channel Kv3.1 was stably transfected in human embryonic kidney cells. Voltage dependence of activation, K+ permeability, sensitivity to external tetraethylammonium, and unitary conductance were similar to Kv3.1 channels expressed transiently in Xenopus oocytes. Kv3.1 channels appear to be regulated because the protein kinase C activator phorbol 12,13-dibutyrate decreased Kv3.1 currents. Based on these results, we find that the stable expression of voltage-gated K+ channels in human embryonic kidney cells appears to be well suited for analysis of both biophysical and biochemical regulatory processes.