We analyze 20 cases of ruptured vertebral artery dissecting aneurysms and discuss the best choices for the surgical procedure. The preoperative Hunt and Kosnik grade was I in nine cases, Ia in four cases, II in three cases, III in three cases, and IV in one case. Rebleeding occurred in six cases, in four cases within 24 hours after the initial bleeding, and in every case within 6 days. In two cases surgery was performed within 3 days after the initial bleeding, in two cases within 4 to 7 days, in 16 cases after more than 7 days. A total of 22 operations were performed in the 20 patients (coating in 12, trapping in 6, proximal clipping of the vertebral artery in 2, clipping of the bleeding point in 2). A case of proximal clipping re-bled 32 days after the operation and subsequently died. Both cases of clipping of the bleeding point were reoperated because of rebleeding and a slipped clip, respectively. All cases in which trapping or coating was performed resulted in a good outcome. Trapping is the most reliable method of preventing rebleed-ing. Coating or proximal clipping is an optional procedure, but cannot always prevent rebleeding be-cause of the continuing circulation.