Extracellular recordings were made of visual unit activity, sustained potential shifts (SPSs), and electroencephalographic activity (EEGs) from the optic tectum and of EEGs from the telencephalon of immobilized toads (Bufo bufo). Moving visual stimuli were presented, and the bioelectric responses were monitored both before and after ligature of the telencephalon. The operation reduced the neuronal spike frequency and the amplitude of the tectal SPS and EEG responses. EEGs were still recorded from the tectum and even the isolated telencephalon. The results are discussed in relation to possible adaptive functions of SPS and EEG changes, the genesis of the EEG, and the role of the telencephalon in visually guided prey-catching behavior.