In recent decades, sporadic cases of ocular Onchocerca species infection have been reported in dogs in the USA and Europe. In the acute stage of the disease severe inflammation of the ocular and periocular tissues was observed. In chronic cases, the strongly coiled, gravid nematodes were incorporated in pea- to bean-sized granulomatous nodules in various parts of the eye, including the retrobulbar space, orbital fascia, eyelid, third palpebra, conjunctiva and sclera. Apart from the ophthalmological significance of the disease, the large number of microfilariae in the skin may be responsible for acute and chronic dermatological problems. The geographical distribution and prevalence of the infection may be greater than currently thought, because the lesions may have been erroneously regarded as other ocular diseases. Onchocerciasis is the world's second most prevalent infectious cause of blindness in human beings and parasitologists have long searched for an experimental model of human onchocerciasis; ocular onchocercosis infections in dogs may provide a useful experimental system.