In a retrospective review about large and giant aneurysms of the literature and the own material (51 large and 19 giant aneurysms) the problems of distribution, diagnosis, and treatment are discussed. The present classification and interpretation are arbitrary and imprecise; size and form, site, origin, and projection have not been taken into consideration. A special analysis and a combined study of large and giant aneurysms are lacking. The own material discussed concerns distribution and classification as well as clinical and neuroradiological findings in the different locations of these aneurysms. The main locations are for large aneurysms ICA (17%), MCA (about 10%), and VBA (about 9%), and for giant aneurysms 3.5%, 3.6%, and 8.6% respectively. The relative distribution for giant aneurysms are ICA with about 50%, ACA with 20%, and VBA with 20% too. The management of giant aneurysms and to a lesser extent of large aneurysms as well is unsatisfactory. The results are discussed. The development of CT-scanning and microsurgery with arterial bypass operations and intracranial artery sutures has improved the therapeutic possibilities tremendously. Some cases are briefly discussed. The prospective personal strategy in handling large and giant aneurysms by direct attack or a combined procedure with external-internal artery bypass operation and a direct occlusion and excision in a second stage have been described. Because of the limited experience, a cooperative prospective study of interpretation, classification, clinical data, course, and therapy of such aneurysms in a representative group of patients is necessary.