In June 1991 a 62-year-old retired man, from Udine (northern Italy), was suddenly affected by dyspnoea. X-ray and CT control detected a coin lesion in the lung, in May 1992 this lesion was removed surgically. Histological examination revealed the presence of a nematode inside an arteriole which had provoked a small infarct in the pulmonary tissue. The parasite presented marked regressive phenomena that made an accurate morphological analysis impossible. However, in the light of certain details of the cuticle, and by analogy with four similar cases occurring in northern Italy, as well as 10 others (nine subcutaneous and one submucosa) reported in man from the same region (Venetia) over the last 15 years, the aetiologic agent was thought to be Dirofilaria (N.) repens. Over all 10 cases of human pulmonary dirofilariasis were reported in Europe: five in Italy, probably by D (N.) repens, two in Germany, in patients coming from Corsica and two in Spain (only by serology), attributed to D. immitis. In addition one case was reported in U.S.A. in a man who previously visited Italy.