Sixteen cases of cerebellar infarction with brain stem compression and tonsillar herniation were studied post-mortem. None was operated. Cardiac embolism was the most common cause (75% of the cases). Infarction involved the superior cerebellar artery territory in 8 cases, and multiple cerebellar artery territories (including in each case the posterior inferior cerebellar artery territory) in 8 cases. It involved the cerebellum only in 10 cases. In the 6 other cases, it was associated with an infarct in the paramedian territory of the brain stem. The oedematous swelling was linked to the large size, the rostral site and the embolic causes of the infarct. Cases with massive infarction of the brain stem differed from others by severe motor weakness of the limbs in 5 cases and a deep coma in the 6th. On the contrary, only one of the 10 cases with lone cerebellar infarct had a mild hemiparesis. Thus, when a hemi- or tetraplegia occurred in the course of an oedematous cerebellar infarction, an associated massive paramedian infarction of the pons must be suspected rather than a brain stem compression. This can be taken into account when a surgical treatment is discussed.