Grapes are an important domestic crop in Iran and are grown mainly for raisins or for the fresh market, together with a limited quantity for wine production. Over 134,000 hectares of grapevines were grown in 1974 (Plan and Budget Organization, 1976) with an average yield of 8.9 tonnes per hectare. The present investigation was undertaken to ascertain whether plant-parasitic nematodes might be one of the factors responsible for the low yield. Dagger nematodes, Xiplzil1cma spp., in general, are regarded as the most important nematode pathogens of grapevines which may cause direct damage to the plant or transmit viruses, and accordingly, investigations were largely confined to this genus.