Evidence is presented for a causal relationship between tobacco ringspot virus and the necrotic ringspot disease of blueberry (Vaccinium corymbosum L.). Tobacco ringspot virus isolates from infected blueberries collected in Michigan, Illinois, and New Jersey were serologically indistinguishable, although differing somewhat in properties. Xiphinema americanum was the only parasitic nematode consistently associated with necrotic ringspot virus-infected blueberries.