A comparison was made of different methods of processing ingesta to release bacteria attached to solid particles, prior to making viable counts. Initially processing was performed under a stream of anaerobic gas and counts were made using the roll tube technique. Later, processing was done in an anaerobic cabinet and counts were made using the plating technique. On long hay diets counts of total culturable and lactate-utilizing bacteria were twice as high with the Stomacher and Ultra-Turrax treatment of ingesta when compared with the Minimal treatment. On the chopped hay and high concentrate diets there was little difference between the processing methods in respect of counts of these two groups of bacteria. Counts of cellulolytic bacteria which are attached to ingesta particles were higher with the Minimal treatment than with the other two methods. In contrast, counts of the ciliate protozoa showed a marked difference owing to processing. Results from the later experiments done in the anaerobic cabinet showed that poor anaerobiosis was responsible for at least some of the lethal action of the Ultra-Turrax and Stomacher.