Since acidosis is a major pathological risk for ruminants, we have defined a new method for the measurement of the intrinsic buffering capacity (BC) of feeds, by modeling the resistance of a feedstuff to the addition of an acid or a base. We compared results obtained on 24 feedstuffs with a strong acid and a strong base to those measured using a weak acid and a weak base which are more physiologically relevant for ruminants. The hierarchy for the BC of feedstuffs did not differ between methods, but results obtained with acetic acid (principal VFA in the rumen) seemed to be the most interesting since they can be integrated in a rumen model. The pH at which the BC were measured influenced their values. Protein content, starch content, water holding capacity (WHC) and intrinsic osmotic pressure of feedstuffs were the chemical and physical variates which best explained the variation in BC of feedstuffs. Initial pH of ingredients varied greatly between feedstuffs and was not related to chemical or physical parameters. Data obtained were in agreement with the literature when similar results were available.