Local edema at the operative bed developed a few hours after uneventful subtotal removal of a lesion occupying the lower medulla and upper cervical cord. The patient experienced apnea, quadriplegia, and circulatory collapse followed by acute respiratory insufficiency. Hydrocephalus secondary to aqueductal occlusion occurred on the 3rd postoperative day. A computerized tomographic scan was compatible with upward transtentorial herniation. The association of this phenomenon with an intra-axial lesion at the cervicomedullary junction has not been previously documented. The pathophysiologial mechanisms implicated in this complication are discussed.