[Hydatidosis of the posterior fossa]

The hydatid cyst is an endemic zoonosis in Spain. The central nervous system is seldom affected, the hydatid cyst in cerebellum being very rare. A patient with hydatid cyst affecting the vermis and right cerebellar hemisphere is presented. The case is described and discussed. The use of CT scan is encouraged as the most worthwhile election of diagnosis techniques. We highlight the need for very careful surgical treatment, preserving the hydatid cyst complete, to avoid relapses and to prevent the change of a benign disease to a chronic one with very high mortality.