Tension pneumocephalus is a rare and severe complication appearing after posterior fossa procedures in the sitting position. This complication may endanger the patient's life and require immediate treatment. However, tension pneumocephalus after neurosurgical procedure in the supine position have been scarcely reported. We report such a complication occurring in a 14-year-old girl submitted to a frontotemporal craniotomy for removal of an astrocytome performed with the patient supine. We discuss ethiopathogenesis and management of this complication.