During the period from January 1975 to December 1988, a total of 28 among 215 cases or 13.0% with multiple aneurysms were seen in the Department of Neurosurgery, Hiroshima University. Classifying by sex, there were 17 males and 11 females with a mean age of 52 years. The number of aneurysms was four in 2 cases, three in 6 cases, and two in 20 cases. By location, there were 13 aneurysms in the anterior communicating artery, 20 in the internal carotid artery, 28 in the middle cerebral artery, 4 in the anterior cerebral artery, and 1 in the posterior inferior cerebellar artery. The incidence of rupture of anterior communicating aneurysm was extremely high being 10 out of 11 cases (90%) followed by that of 3 out of 4 cases (75%) for the anterior cerebral aneurysm. Although the number of cases undergoing surgery during the acute stage has been increasing, there was an unexpectedly long waiting period from onset of the initial symptom to surgery averaging 23.6 days. As a rule, clipping was undertaken for the treatment of ruptured aneurysm. For non-ruptured minor aneurysm, coating and wrapping were sometimes performed to reinforce the aneurysmal wall. All the aneurysms were treated through a single craniotomy simultaneously in 13 cases, by two craniotomies in one day in 10 cases, and by two craniotomies on separate days in 5 cases. The results of surgical treatments were satisfactory in all the cases except for a female who expired following surgery due to vasospasm and GI bleeding.