Objective: Aneurysms arising from the posterior inferior cerebellar artery(PICA) are uncommon. We review literature on that and surgical results on aneurysmal treatment by choice of surgical approach. Methods: On the basis of radiologic findings & charts, we review retrospectively the surgical results of 12 cases from Mar 1999 to Dec 2003. Results: The mean age of the 12 patients was 55.8(ranged from 36 to 71) and female was predominant (female:male = 8:4). Locations of PICA aneurysms revealed variously(vertebral artery - PICA junction: 8, lateral medullary segment: 2, PICA - anterior inferior cerebellar artery common trunk: 1, telovelomedullary : 1). Surgical approaches & treatments were attempted in 11 cases and embolization was done in 1 case(Far lateral transcondylar or supracondylar approach & clipping: 9, Far lateral transcondylar or supracondylar approach and trapping: 2, suboccipital approach & clipping: 1). The surgical result were 8 of 12 patients were good outcome, 1 of 12 was severely disabled and 3 of 12 were died. Conclusion: First, we choose surgical approach by the laterality of aneurysms and surgical or interventional treatment is attempted as soon as possible. The PICA aneurysm is regarded as having a relatively good surgical outcome without drilling of the posterior arch of the atlas.