This study assessed the blood flow and histological changes of an animal model of arteriovenous malformation (AVM) over 84 days in 71 rats, and compared the histological findings to 17 specimens of human AVM. Carotid-jugular fistula blood flow positively correlated with time. The maximum flow rate occurred at 42 days, at which time the nidus was considered mature and was histologically similar to human AVMs. Morphological similarities between the model and human AVM vessels included heterogeneously thickened walls, splitting of the elastic lamina, thickened endothelial layers, endothelial cushions, lack of tight junctions, loss of endothelial continuity, endothelial-subendothelial adherent junctions, and luminally directed filopodia. These findings support the theory that vascular changes in human AVMs are secondary to increased flow and provide a basis for using this model in studies of AVMs.