SUMMARYField trials in south eastern counties of England over the period 1967‐72 have been carried out on sites infested by the cereal cyst‐nematode,Heterodera avenae.In the main, spring barley was the cereal used, since this is the dominant cereal grown, and during this period resistant cultivars became available. Behaviour of soil populations of this nematode was erratic, but resistant cultivars from the Welsh Plant Breeding Station, based on Rika/Proctor, consistently lowered the nematode population in the soil, and outyielded more modern susceptible cultivars on infested soils. Evidence was found, in 1972, of a reduction in viability of cysts, associated with dise