There is continuing controversy about the benefits of decompressive craniectomy for the treatment of massive infarction of middle cerebral artery (MCA) territory. Under conservative therapy, the mortality rate for this stroke is reported to be up to 80%. So the authors have actively carried out decompressive craniectomy since 1997, and have compared the outcome with patients who were admitted before 1997 and, consequently treated with conservative therapy. Fifteen consecutive victims of massive infarction of MCA territory were studied. Seven patients (male: 1, female: 6, mean age: 79.8 years) were treated with conservative therapy, and 8 patients (male: 3, female: 5, mean age: 71.8 years) were treated with decompressive craniectomy. There were no significant differences in age and consciousness level distribution between the two groups. Mortality rate in the conservative therapy group was 85.7% against 12.5% in the surgery group (p < 0.05). Functional performance, which was evaluated by activity in daily life (ADL), was also better in the surgery group e.g. 3 patients in ADL 3, and 3 in ADL 4 (1 patient died from a non-neurological cause). Even among the patients with speech-dominant hemispheric stroke, all except one were able to communicate in some way and understand language. Even though patients in this study were elderly, decompressive craniectomy reduced mortality and improved functional performance, so it seems that this surgery should be aggressively considered for massive infarction of MCA territory.