Amorphous Cd–Sb films with a Cd content of about 20% can be switched from a high-resistance state to a low-resistance state by the application of a dc or pulsed bias. Microanalysis of the switched region and observation of the growth of the dendritic filament from the negative electrode suggest that the migration of Cd ions is responsible for forming a conducting channel in the memory switching. The mechanism of the memory switching is explained as follows. First, a Cd speckle appears at the negative electrode, and then Cd dendrite develops from it. When the Cd dendrite just bridges both electrodes, a large current flows and the thermal effect extends to the surrounding region, creating a channel.