1. Bilirubin conjugation in rat liver slices was reassessed by using analysis of ethyl anthranilate azopigments to estimate separately the formation of bilirubin mono- and di-glucuronides. 2. Conjugation in slices resembles the situation in vivo more closely than does microsomal conjugation, in that diglucuronide is formed in appreciable quantity. 3. Both bilirubin mono- and di-glucuronides were present in slices in approximately equal amounts, but the monoglucuronide was the major product found in the incubation medium. 4. These results are discussed in relation to recent theories on the relationship between bilirubin mono- and di-glucuronide formation in vivo.
