Patients who undergo endovascular repair of aorto-iliac aneurysms (EVAR) require internal iliac artery (IIA) embolization (IIAE) to prevent type II endoleaks after extending the endografts into the external iliac artery. However, IIAE may not be possible in some patients due to technical factors or adverse anatomy. The aim of this study was to assess retrospectively whether patients with aorto-iliac aneurysms who fail IIAE have an increase in type II endoleak after EVAR compared with similar patients who undergo successful embolization. We retrospectively analyzed the records of 148 patients who underwent EVAR from December 1997 to June 2005. Sixty-one patients had aorto-iliac aneurysms which required IIAE before EVAR. Fifty patients had successful IIAE and 11 patients had unsuccessful IIAE prior to EVAR. The clinical and imaging follow-up was reviewed before and after EVAR. The endoleak rate of the embolized group was compared with that of the group in whom embolization failed. After a mean follow-up of 19.7 months in the study group and 25 months in the control group, there were no statistically significant differences in outcome measures between the two groups. Specifically, there were no type II endoleaks related to the IIA in patients where IIAE had failed. We conclude that failure to embolize the IIA prior to EVAR should not necessarily preclude patients from treatment. In patients where there is difficulty in achieving coil embolization, it is recommended that EVAR should proceed, as clinical sequelae are unlikely.