This report concerns a clinicopathological study of three additional patients with corticobasal degeneration (CBD), described here for the first time, and a clinicopathological correlation between pyramidal signs and upper motor neuron involvement, in ten autopsy cases of CBD, including seven cases reported by us previously. We investigated pyramidal signs, including hyperreflexia, Babinski sign, and spasticity, and involvement of the primary motor cortex and pyramidal tract, focusing on the astrocytosis of the fifth layer of the primary motor cortex. Pyramidal signs were observed in six (60%) of the ten cases. Hyperreflexia was evident in six patients (60%), with spasticity being observed in three patients (30%). Loss of Betz cells associated with prominent astrocytosis and presence of ballooned neurons in the fifth layer of the primary motor cortex was observed in all ten cases. In all cases, involvement of the pyramidal tract was obvious in the medulla oblongata, without involvement of the pyramidal tract in the midbrain. Constant and severe involvement of the fifth layer of the primary motor cortex, including the Betz cells, has not previously been reported in CBD. We suggest that the pyramidal signs in CBD have been disregarded.