This study is concerned with cytochrome P-450 contents and different forms of cytochrome P-450 after administration of hydrocortisone in common bile duct ligated and adrenalectomized rats. Content of total hepatic cytochrome P-450 is decreased after either common bile duct ligation or adrenalectomy. In contrast, hydrocortisone increases content of hepatic cytochrome P-450. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis was used to examine the poly-petide pattern of rat liver endoplasmic reticulum membrane fraction. This report describes the chromatographic separation of four forms of microsomal cytochrome P-450 apoproteins, whose molecular weights ranging from 50,000 to 58,000 indentified in a sodium dodecyl sulfate(SDS)-6M urea-polyacrlamide gel electrophoresis system. Bile duct ligation was associated with a reduction in band I,II,III and IV. And administration of hydrocortisone after bile duct ligation plus adrenalectomy demonstrated a return of band II and III. Hydrocortisone administrated alone increased band III, while band 1 was decreased.