Many synthetic coating materials had been reported in the literature. One of them, ethyl, 2-cyanocrylate is known to the most avaliable material in coating aneurysms. We have recently used it in the treatment of 5 cases of intracranial aneurysms at various sites with successful results, and in following situations much advantages and need seem to be there. First, reinforcement of incomplete simple aneurysmal clipping because of each shape, configuration, site, broad neck and surrounding vital vessels which enter and leave the aneurysmal sac. Second, under surgical microscopic field, to reinforce the incidental microaneurysm, the local thining and dilation of regional arterial well. And last, for preventing of the possible slipping of clip in itself.