The present invention relates to a method for preparing a fecal 5 microbiota sample of a donor subject. Said method includes the following steps: a) collecting at least one fecal microbiota sample from the donor subject; b) within a period of less than 5 minutes after collecting the sample, placing said sample obtained in step a) in an oxygen-tight collection device; c) mixing the sample obtained in step b) with at least one aqueous saline 10 solution containing at least one cryoprotectant and/or a filling agent; d) optionally, filtering the mixture obtained in step c), in particular by means of a filter comprising pores having a diameter of less than or equal to 0.7 mm, preferably less than or equal to 0.5 mm; and e) storing the mixture obtained in step c) or d) by freezing said mixture at a temperature 15 of between −15° C. and −100° C. Steps b) to e) are carried out in anaerobiosis.
