During 1990 we treated 49 cases of arterio-veinous malformations (AVMs) using radiosurgery. We employed 15 MV X-Ray minibeams of a Saturne 43 Linac, eight additional collimators, 6-20 mm, the O Betti armchair and the Talairach stereotactic frame. Irradiation consisted of delivering 25 Gy at the periphery of the nidus corresponding to the 60-70% peripheral isodose range. We used the "Associated Target Methodology" and the three-dimensional treatment planning system Artemis-3D, both of which have been developed in our radiotherapy department. In December 1992, 44 out of 49 patients who had been treated were available for analysis with a 2-3-year follow-up. The overall obliteration rate was 33/44 (75%). According to the number of isocenters the obliteration rate was: 22/26 (85%) for one isocenter. In 18 multi-isocenters irradiation cases overall obliteration rate was 11/18 (61%). Two isocenters were used in nine of these 18 cases, the obliteration rate was 6/9; while when three isocenters were used it was 2/4 and in five cases of four isocenters irradiation the obliteration rate was 3/5. Obliteration rate for lesions < or = 4200 mm3 was 31/37 (84%). For greater volumes (5500 mm3 to 19000 mm3; median 9200 mm3) the obliteration rate was 2/7 whereas three others were partially (75 to 90%) obliterated and two remained inchanged. Before radiosurgery 21 cases received other treatment (mostly embolizations), the obliteration rate in this group was 15/21 (71.5%) while in previously untreated AVMs it was 18/23 (78%). A control arteriography was performed between 6 to 18 months after radiosurgery in 44 patients; three others refused the arteriography but are alive and well; two others had palliative irradiation, one of whom is dead. Out of 28 AVMs checked between 6 to 12 months 17/28 were obliterated (61%). In four cases, epilepsy was the first symptom; one has not suffered a further crisis whereas three others experienced a decrease in the number of crises. Two patients had recurrence of bleeding four and six months after irradiation (recurrence rate 2/44 = 5%). There were no lasting neurological consequences.