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Samples of the diets of oesophageally fistulated sheep and cattle grazing a semi-arid chenopod shrubland dominated by bladder saltbush (Atrip!ex ~'esicaria Hew. ex Benth.) were collected over a four year period. Seasonal condiiions varied from very wet to near drought. The diets of the two herbivores were different on all sampling occasions. However, it can be generalized that overall, sheep had a greater grass component in their diets and that cattle in compensation ate more saltbush than did sheep. Both sheep and cattle exhibited considerable diet selectivity and flexibility. Exact relationship between the measure of forage on offer and the proportions of any plant group in the diet could not be determined from the data collected in this experiment. However, hirearchies of preference were established. The differences in digestibility and nitrogen content of the diets between the two herbivores were appreciable with sheep mostly selecting a diet of higher digestibility and nitrogen content. The implications of these data for animal production and rangeland management are discussed.