1. An account is given of the lesions caused by Cordophilus sagittus infestations of an African buffalo, a bushbuck and 18 kudus.
2. The distribution of adult parasites and the host response in the kudu are given in detail.
3. Adult worms appeared most frequently in medium-sized and small branches of the pulmonary arteries, less frequently in coronary veins and only occasionally in the right ventricle.
4. Aneurysms filled with parasites and showing a rather remarkable proliferative intimal reaction frequently appeared in the coronary veins and in the medium-sized and small branches of the pulmonary arteries.
5. Non-aneurysmic segments of the pulmonary arteries also reacted to the parasitic infestation. This manifestation might be summed up as a "proliferative polypoid villose verminous endarteritis".
6. Attention is drawn to the close resemblance between this manifestation and certain types of reactions in the pulmonary arterial tree of dogs caused by another filarial worm, Dirofilaria immitis.
7. The possible significance of the lesions described above as a health problem in wild ruminants is discussed.
8. Knowledge on the incidence of C. sagittus infestation in cattle and buffalo appears to be restricted to single cases in each. Careful examination of the myocardium of these species when the opportunity avails itself may yet reveal a higher morbidity rate.
9. It is proposed that the derivative from the generic namely, "Cordophilosis " be used for the disease.