Oslerus osleri is a metastrongle whose first-stage larvae are expectorated by the bitch, and which are infecting for pups; few cases are described from France. The biological features of this parasite, diagnosis and therapy are described in a first bibliographic part. 29 of 66 dogs examined were infected with Oslerus osleri. We investigated the cause of their chronic coughing, which was not cured by routine therapies. Several diagnostic methods were used, of which endoscopy was the best. The following drugs were used to treat infection with Oslerus osleri: ivermectin, levamisole, oxfendazole and fenbendazole. The last-mentioned two drugs are safe for dogs and very effective against this parasite.