A series of 7 cases of PCA aneurysm treated between 1978 and 1992 were analytically reviewed together with 79 cases culled from the literature. In comparison to those localized elsewhere, PCA aneurysms are more frequently large, more frequently present with tumour-like symptoms and appear at an earlier age. Surgical outcome was evaluated in relation to clinical onset, site and size of the aneurysm, the surgical procedures adopted for excluding it and pre-operative clinical grading appeared to influence outcome. The fact that site, size and surgical technique do not significantly influence prognosis is probably due to the rich collateral flow present in the areas fed by the posterior cerebral artery. The authors conclude that, clinically speaking, PCA aneurysms should be considered as a separate group.