The therapeutic options for arteriovenous malformations (AVMs) of the thalamus and the basal ganglia have expanded to include preoperative embolization, stereotactic radiation, and microsurgery. Adjuncts to surgery such as stereotactic guidance, electrophysiological monitoring, intraoperative ultrasound, intraoperative angiography, and induced hypotension have significantly reduced postoperative morbidity. We review the management and outcome of 65 consecutive patients who were treated for deep-seated supratentorial vascular malformations; 45 patients (69%) were treated surgically, 10 patients (15%) were treated conservatively, and 10 patients (15%) underwent radiosurgery. This retrospective study (1976-1993) includes 51 AVMs (78%), 14 cavernous angiomas (22%), and 10 associated vascular anomalies (15%). Initially, 59 (91%) of 65 patients presented with hemorrhage; 23 patients (39%) suffered recurrent hemorrhages. Malformations ranged in size from 1 to 7.5 cm (mean, 2.8 cm). AVMs were fed principally by the anterior and posterior choroidal, thalamoperforate, and lenticulostriate arteries. Venous drainage was uniform via the deep venous system. Among 39 patients who underwent surgery for AVMs, 26 (67%) improved, 7 (18%) remained unchanged, 5 (13%) worsened, and 1 (3%) died. Among six patients who underwent surgery for cavernous angiomas, four (66%) improved, one (17%) remained unchanged, and one (17%) worsened. Operative complications included transient neurological deficits in seven patients (16%), permanent neurological deficits in six patients (13%), and new bleeding from residual AVMs in four patients (9%). Among 10 patients treated conservatively, 3 (30%) had repeat hemorrhages, 2 (20%) had progressive neurological deficits, and 1 (10%) died.(ABSTRACT TRUNCATED AT 250 WORDS)