Extracellular activity in the red nuclei in different behavioural states was investigated in control adult rats and in adults rats who had previously undergone a cerebellar hemispherectomy on their 2nd, 5th, 10th or 20th day. In addition to visual analysis, spectra and coherence functions were computed from the signals during quiescence and movements. Preceding and during movements a particular pattern, characterized by a regular rhythm between 7.5 and 8.0 Hz occurs. Inter-rubral coherences are high at the specific pattern frequency. In rats with a cerebellar hemispherectomy - irrespective of the age at lesioning - power spectra from both red nuclei differ markedly from each other during quiescence. When movements occur, rats operated at the 20th day show a pattern in both red nuclei similar to that found in control rats. However, in rats lesioned at the 5th or 10th day the specific pattern frequency is much lower while in rats operated at the 2nd day no specific patterning of red nuclei activity is evident.