This is a retrospective study on wild raptors submitted to the Universitéde Montréal (Quebec, Canada) from 1989 to 1996. Cyathostoma spp. (Nematoda: Syngamidae) adults and/or eggs were found in air sacs, lungs, bronchi, and trachea of 12 raptors (Falconiformes and Strigiformes) from Quebec, Canada, belonging to eight different species, five of which are first host records for this parasite: barred owl (Strix varia), snowy owl (Nyctea scandiaca), northern harrier (Circus cyaneus), northern goshawk (Accipiter gentilis), and broad-winged hawk (Buteo platypterus). The infection was considered fatal in four birds, while no significant clinical signs were observed in the other cases. Major pathologic changes included diffuse pyogranulomatous air sacculitis, pneumonia, and bronchitis. A few unidentified larval nematodes embedded in a granuloma were found in the lungs of an additional Coopers' hawk (Accipiter cooperii); they were not considered clinically significant. A dead nematode, surrounded by necrotic inflammatory cells, was found in the air sac of a northern goshawk. The presence of nematodes in air sacs or lungs should be considered in wild raptors demonstrating respiratory problems.