Using CDW data from 5 tertiary hospitals in Korea, this study identify the optimal range of trough level that can prevent adverse outcome in the early periods after transplantation.

Inclusion Criteria:

• Renal transplant recipients between January 1, 2005 through December 31, 2014 in one of the five participating centers
• Patients receiving oral tacrolimus as one of the main immunosuppressant at the start of the defined cohort time (i.e. at post-transplant 2 months for the analysis of 1-year outcomes and at post-transplant 12 months for the analysis of 6-year outcomes)

Exclusion Criteria:

• Graft failure occurring within the first 2 month of transplantation
• Mortality of any cause occurring within the first 2 month of transplantation
• Patients moving centers during the study period
• Patients who have received other organ transplantation(s) besides renal transplantation in the defined period

All renal transplant recipients between January 1, 2005 through December 31, 2014 in one of the five participating centers are included. Further selection will be undertaken to include only patients receiving oral tacrolimus as one of the main immunosuppressant at post-transplant 2 month (for early outcomes) and post-transplant 1 year (for late outcomes).