1. It was shown that adult germfree rats did not excrete detectable amounts of phenyl sulphate and indoxyl sulphate. Total urinary excretion of phenol by this type of animal was also low. 2. Urinary excretion of a large number of other ester sulphates was uninfluenced by bacterial activity in the gut. 3. No difference in the activity of liver enzymes sulphurylating phenol and dehydroepiandrosterone was found in germfree and conventional rats within the same age group. Nor were there differences between these 2 types of rats with respect to the capacity of their sulphate-activating liver enzymes.