Guglielmi detachable coil (GDC) treatment for complicated cerebral aneurysms is an attractive option that has become widely accepted in recent years. This technique is usually considered only if the patient harbors an aneurysm that is not a good candidate for surgical clipping. However, the definition of "surgical candidate" varies among institutions, and many patients worldwide are being treated with GDCs as primary therapy. Although most centers currently perform follow-up angiography at 6 months to 1 year, others do not routinely perform it after an initially good result. The authors present a case that indicates longer follow up may be necessary and illustrates some of the pitfalls of GDC treatment. This 56-year-old man presented to the emergency room with a Hunt and Hess Grade II subarachnoid hemorrhage and was found to have a wide-necked basilar apex aneurysm. Because of associated medical comorbidities, it was decided to treat the aneurysm with endovascular techniques. The patient did well on follow-up angiography at 1 year postprocedure. However, at approximately 2 years follow up, the aneurysm was demonstrated to have dramatically recanalized and regrown, requiring open surgical intervention. Endovascular coiling was insufficient to treat this aneurysm and complicated definitive surgical management because a large coil mass had been placed in the operative field. It can be inferred from this case that angiographic follow up of these types of lesions may be beneficial up to 2 years after GDC treatment.