Thirty specimens of the pampas fox (Dusicyon gymnocercus) were injected with Neoprene latex to study the distribution of the internal carotid and vertebral arteries, and their derived vessels, on the ventral surface of the brain. The internal carotid artery and its rostral and caudal branches were single on both sides in all cases, as was the right middle cerebral artery; the corresponding left artery was single in 96.7% of the cases and double in 3.3%. The right rostral cerebral artery was single in all cases, and single (96.7%) or absent (3.3%) on the left. The rostral communicating artery was present in 96.7% and absent in 3.3%, while the right caudal cerebral artery was single in 86.7% and double in 13.3%, but only single on the left. The basilar artery was single in all cases. The cerebral arterial circle was closed rostrally in 96.7% of the cases and open in 3.3%, but was closed caudally in all animals. The encephalon blood supply was derived principally from the carotid system, but also from the complementary vertebral-basilar system.