Although it's been about 100 years since the vascular malformation was first discovered, it is very recent situation that the natural history of cavernous malformations is being clarified. Once it was considered to be very rare, but the introduction of MRI made it possible to diagnose more asymptomatic patients than ever. With this sophiscated tool, it become easy to diagnose and follow up this vascular disease. As more and more asymptomatic or minimally symptomatic patient are being discovered, it become very difficult part for a neurosurgical surgeon to choose the method of treatment in each clinical case. A great deal of recent controversy has been generated concerning the best surgical approach to treat benign lesions that are associated with epilepsy. Since the definition of the bleeding and the clinically significant symptom are different from author to author, one should be careful to recognize the statistical numbers of the from articles. We reviewed dozens of articles to figure out the right indication, approach and microsurgical technique. The surgical risk should be carefully weighed against the morbidity from the natural history of the disease.