Results of the hrst year of the prospective study are presented. The balic motto was immediate treatment of an aneurysm (AN) with irrespective of time and the patienťs condition. Interventional treatment was always considered and attempted first. During 2000 a total of 104 procedures in 82 patients were implemented. 62 procedures were interventional, 13 of them only attempts, in 6 cases surgery followed immediately, in 3 cases repeated intervention was successful, 1 AN thrombotized spontaneously after the interventional attempt, 3 AN were left untreated. Therapeutic procedures were possible in 46 patients in 49 sessions, a total of 50 AN were treated. 43 AN were coiled, 6 parem arteries (VA or ICA) were occluded, 1 fusiform AN was treated by stenting. In 42 operations a total od 49 AN were treated. In 34 surgical operations 38 AN were clipped. In 5 patients a parem artery was occluded (8 AN). One giant ophthahnic AN was resected after intravascular parem artery occlusion. The last 2 AN were resected in one operation. Twelve poor results (MM) in 104 procedures represent a MM rate of 11.5 %, if 13 endovascular attempts are deducted the MM rate was 13.5 % (12 of 89). Total MM of interventions was 4.8 % (3 of 62), deducting 13 attempts with 0 % MM, therapeutic procedures (n = 49) MM was 6.1 % (3 of 49). In surgical procedures (n = 42) the MM rate was 21.4 % (9 of 42). In 5 of 43 coiled AN sack/neck remnants were seen on the immediate porstprocedural angiography (11.6 %). All 38 clipped AN in 36 surgeries were clipped without remnants. Factors considered in the decision-taking process. 1. Presence versus absence of SAH. Unrnptured AN are from the general, not technickl point of view, more suitable for an endovascular approach. 2. Patienťs condition. Patients in HH 4 and 5 without intracerebral haematomas are preferably treated by coiling. 3. Patienťs age and general condition. In older patients coiling is prefered. 4. AN location and configuration are individual factors. 5. AN size. Large and giant AN are difficult to trest with coiling. In conclusion, with the use of interventional techniques the MM rate can be cut by half at the price of doubling the technical failure of AN exclusion.

        Key words: aneurysm, surgery, coiling