It is a recognised fact that the potato-strain of the eelworm Heterodera schachtii is distributed from district to district by the agency of cysts embedded in soil adherent to seed tubers. The need for some method of freeing seed tubers from viable eelworm, and the extent to which infection may be carried by seed grown in eelworm infested land, are strikingly illustrated by observations carried out by the staff of the Ormskirk Potato Testing Station, which, by permission of the Director of the National Institute of Agricultural Botany, are quoted here.