The paper gives results of tests of new, two-stage pilot scale ESP system, consisting of a precharger and a downstream collector, on a high-resistivity flyash at a coal-fired power plant. Operating on a 0.47 cu m/s slipstream, the system had a specific collecting area of 50.4 sq m/cu m sec. With an inlet mass loading of 18 g/cu m, and a dust resistivity of 1.97 x 1011 cm, an overall average collection efficiency of 97.7% was achieved. When the precharger was turned off, a collection efficiency of 83.4% was recorded. Although the plate area of the precharger is only about 3% of that of the entire system, the effect of energizing the precharger is approximately equivalent to doubling the collecting area of the system.