We report the presence of ballooned neurons (BNs) in the cerebral cortex of patients with progressive supranuclear palsy (PSP) using immunohistochemistry for phosphorylated neurofilament in addition to standard histologic staining methods. In six of the nine patients studied. BNs were seen in the cerebral cortex. In two of these six patients. BNs were abundant and cortical degeneration was present in the precentral cortex. On immunohistochemistry. BNs were positive for phosphorylated neurofilament and alpha B crystallin, and some BNs were positive for ubiquitin and tau protein. The immunohistochemical staining pattern was similar to that of the BNs seen in other diseases, such as corticobasal degeneration. The presence of cortical BNs does not differentiate PSP from corticobasal degeneration although BNs are fewer in the patients with PSP when cortical degeneration is not present.