The rapid delayed rectifier, I_Kr is believed to have h‐erg (uman ther‐à‐go‐go elated ene) as its molecular basis. A recent study has shown that rectification of h‐erg involves a rapid inactivation process that involves rapid closure of the external mouth of the pore or C‐type inactivation. We measured the instantaneous current to voltage relationship for h‐erg channels using the saponin permeabilized variation of the cut‐open oocyte clamp technique. In contrast to C‐type inactivation in other voltage‐gated K⁺ channels, the rate of inactivation was strongly voltage dependent at depolarized potentials. This voltage dependence could be modulated independently of activation by increasing [K⁺]_o from 2 to 98 mM. These results suggest that inactivation of h‐erg has its own intrinsic voltage sensor.