Samples of CSF collected from 20 normal healthy calves were analysed either immediately or after having been stored for 24 hours at 4 degrees C in the presence of 11 per cent autologous serum. There were no significant differences between the total and differential cells counts of the fresh and stored samples, but there was a positive linear correlation between them. There were some morphological changes to the nuclei of the mononuclear cells in the stored samples.