We have experienced 21 cases with ruptured cerebral aneurysms in the posterior circulation during the last 10 years. Nine were male and twelve were female patients . Mean age was 52. We classified these cases into three groups: 1) Basilar artery aneurysms (BA) , 2) Aneurysms at the junction of the vertebral and posterior inferior cerebellar arteries (PICA), and 3) fusiform aneurysm of the vertebral artery (VA). Eleven cases were included in the BA group . Nine had aneurysms at the basilar

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... summit and two at the junction of the superior cerebellar artery . We performed aneurysm clipping in five cases. Surgery had been done between 8 days through 45 days (mean 22 days) after the SAH attacks. There were two cases with excellent results , two with good results and one with fair. Five out of six non-surgical cases died; three due to severe SAH attack , one due to rebleeding and one due to respiratory complication. The PICA group comprised eight cases , half of whom had experienced clipping surgery. One case had undergone exceptional surgery on Day 1; while the other three had surgery on Day 8, 13, and 16 respectively . Two had excellent results, one fair and one died (operative failure). All four non-surgical cases died , two due to severe SAH, one due to vasospasm and one due to rebleeding. There were two VA cases . Both had been treated by ligation of the origin of the vertebral artery. Follow-up results were good . As a rule, we have treated patients with ruptured cerebral aneurysms in the posterior circulation by so-called delayed operation. The surgical results have been good in two thirds of the cases , and the mortality rate was 11%. Two patients died of rebleeding while waiting for radical surgery . We conclude that early surgery could be considered , especially in good grade cases, to avoid rebleeding. Development of microsurgical techniques , intraoperative monitoring systems and brainprotective drugs, etc., would make early surgery possible in cases with ruptured aneurysms in the posterior circulation.