Symptoms characterized by buds and new shoots mortality, cankers on branches and trunks, leaf spots, dark brown spots on nuts, and bacterial exudate on necrotic lesions, were observed on fouryear- old filbert trees (Corylus avellana L.) c.v. Barcelona, during 1985, at the Carillanca Exp. Sta. (INIA, Temuco). A Xanthomonas sp. was isolated from the infect.ed tissue. In the pathogenicity test, under laboratory conditions, field symptoms were reproduced on buds and leaves of young filbert trees. The bacterium was identified as Xanthomonas campestris pv. corylina (Miller, Bollen, Simmons, Gross, and Barss, 1940) Oye 1978. Syn. X. corylina (Mi Iler et al.) Starr and Burkholder, causal agent of bacterial bl ight of the filbert. In a survey in the IX Region during 1986, the disease was also observed on old filbert trees, but they were less affected. The bacterium was kept at the Commonwealth Mycological Institute, London, under the numbers B11422 and B11688.