During 1982, numerous plants with concentric brown leaf spot, cankers, and black rot in stems, bud and floral blight, and dead plants, were detected on lupine fields. ln some areas of the IX Region, this problem caused the loss of complete fields. The lmperfect fungus Pleiochaeta setosa (Kirchn.) Hughes was isolated from plants with these symptoms. It produces conidia with four to eight septa; the middle cells were clear brown and the twa end celIs were hyalines to light brown; the conidia sizes varied between 60 to 90u in length and 14 to 22u in diameter; from the terminal celI sprouted one to four hyaline setae. From the isolations, mycological observations, and pathogenicity tests, it was concluded that “brown spot” is present on lupine fields, of the IX Region of Chile. This is the first confirmed report of this fungus affecting lupine in the country.