SUMMARYSix potato cultivars with different levels of resistance to the white potato cyst nematode (PCN)Globodera pallidaPa2 were grown for three seasons in field plots to whichG. pallidaPa2 cysts had been introduced earlier. There were two planting times, corresponding to early and maincrop commercial planting times, and two initial PCN population densities, high and low.The effect of cultivar on PCN population density was far greater than the effect of planting time or initial nematode population. The final PCN populations for the cultivars Ilam Hardy, Wha, 4696A(2), Sovereign, D40/6 and V390 were 151, 74, 27, 1.4, 0.2 and 0.06 eggs per g of soil respectively.It is concluded that resistant potato cultivars can be very effective in controllingG. pallidaPa2 in the field.