The presence of the reduction products of bilirubin and the so-called 380 mu-substance of Ostrow in C-bile obtained by a duodenal tube from 3 cases of Gilbert's syndrome treated with phenobaribital was studied. The results are briefly summarized as follows.
1. During the administration of phenobarbital mesobilirubin was detected in the C-bile of all the three cases and dihydromesobilirubin in one of them.
2. Likewise during the treatment the so-called 380 mu-substance of Ostrow was observed markedly in the C-bile. The 1-3 spots of the paper chromatograohy proved to be negative to the pentdyopent test, but the 4-7 spots were positive. The absorption maxium of the 5-7 spots after the diazo reaction was at 540-530 mu, and the absorption maximum of azo dye of the spot 4 was around 520 mu which coincided with that of azo dye of Gunn rat.
3. Among the important factors that induce the decrease in the serum Bilirubin level the findings stated in the preceding items seem to play an important role, in addition to the acceleration of the synthesis of Bilirubin glucuronide.