In spite of great success in the treatment cerebral AVMs with stereotactic radiosurgery, the role of this treatment modality in angiographically occult vascular malformations (AOVMs) is not recognized. Since the installation of the Gamma-knife, we have treated 20 cases of AOVMs by radiosurgery. There were 13 males and 7 females, the age ranged from 3 to 58 years with an average age of 34.0 years. Their clinical presentations at the onset were haemorrhage in 11, convulsive seizure in 7 and progressive neurological deficits in 2. Two cases had multiple lesions. Among 20 symptomatic lesions, 14 were located supratentorially, 4 in the brain stem and 2 in the cerebellar hemispheres. Following localization with MRI and dose planning, the lesions were treated by radiosurgery and the doses ranged from 15 to 20 Gy at the margins. Follow-up studies indicate a significant control of rebleeding as well as of the convulsive seizure. Imaging studies demonstrated the shrinkage of the lesion in 3 and reduced enhancement with Gadolinium-DTPA in some others. Adverse effects, chiefly related to radiation-induced oedema, occurred in 5. But they were generally mild and well controlled by medication. Thus the preliminary results indicate a certain usefulness of radiosurgery in the treatment of symptomatic AOVMs.