Abstract
Conjugated and unconjugated bilirubin can be stained and separated histochemically by a method using diazotized 2,4-dichloroaniline. In cholestatic human liver both pigments are demonstrable. Icteric human kidney in which bilirubin is predominantly conjugated and Gunn rat papillae containing only unconjugated pigment were used to confirm the validity of the histochemical method. Furthermore, homogenates of cholestatic liver were treated as in the histochemical method; the azo pigments formed were identified by thin layer chromatography and correspond to azo pigments formed from known conjugated and unconjugated bilirubin.