We present the case of a 41-year-old man with a vascular network associated with the left posterior cerebral artery (PCA). Although initially considered to be a brain AVM, further investigation showed no arteriovenous shunting and a rete mirabile of the PCA was diagnosed. A well known but rare occurrence mainly in the anterior circulation, rete mirabile has not previously been described in the PCA.The PCA is a composite vessel, developmentally. Its proximal portion derives from the posterior division of the ICA while its cortical territories are annexed from the anterior choroidal artery adjacent to the lateral geniculate body. We propose that this rete (or network) represents a persistence of the embryonic anastomosis betweenthe AChA and the PCA.