We report the use of an N-butyl-2-cyanoacrylate (NBCA) mixture for embolisation of six cases of carotid aneurysm after detachable balloons, and/or microcoils had been placed in the aneurysm. The mixture was injected into the aneurysm to prevent delayed bleeding or distal migration of the balloons, or microcoils. No subarachnoid haemorrhage or distal migration of the balloons or microcoils occurred up to 4.5 years after embolisation. Reflux of the NBCA mixture into the parent artery occurred in one patient, who had a neurological deficit which recovered in a month. NBCA mixture may be useful in embolisation of intracranial or skull base arterial aneurysms, for reducing the size of remaining lumen in an aneurysm at high risk of rebleeding which accommodate no more balloons or microcoils, or preventing possible delayed migration of balloons or microcoils. However, prevention of leakage of the mixture into the parent artery remains a problem.