The purpose of this study is to demonstrate that the biliary concentration of TCR is a good marker of its immunosuppressive activity.

Inclusion Criteria:

• Adult patients (> 18 years) of both sexes,
• Candidates for liver transplantation or retransplantation, whatever the etiology and severity of the underlying disease,
• Not having expressed their opposition to participation in the study

Exclusion Criteria:

• Bilio-enteric anastomosis,
• Associated transplantation of another organ
• Contraindications to TCR administration
• Delayed introduction of TCR (beyond the 5th postoperative day) whatever the cause.

liver-transplanted patients who receive tacrolimus