The behavior of an arc in the cathode region of a high-pressure, high-current arc heater is investigated numerically. The study is conducted to determine the design features required for high-performance arc heaters needed for future aerospace research facilities. Computations are performed for operating pressures in the range 50-200 atm and load currents in the range 6000-18,000 amp. At high pressures, due to the high-current carrying capability of the dense gas, spot size remains reasonably small, even for high-load currents. Its value is 1.1 mm for a 50-atm arc with a load current of 18,000 amp. By increasing pressure, it can be reduced further. Smaller spot size may allow us to design thinner electrode rings. Spot temperatures are high enough to cause ablation of the electrode material. In order to reduce material ablation at very high currents and prolong electrode life, the operating pressure must be high and the arc should be rotated. Experimental studies to compare with these results would be desirable.