Dosing of tacrolimus is challenging due to the large inter-individual variation in its pharmacokinetics. The investigators have developed a pharmacokinetics population model that can be used to estimate individual doses of tacrolimus in renal transplant recipients. The model will be prospective tested in a randomized clinical trial.

The hypothesis is that the computer model is superior to experienced transplant physicians in reaching and keeping the patients in the target range of tacrolimus.

Patients will be randomized to either computer or standard dosing strategies at time of transplantation or as early after transplantation as possible in case of deceased donor transplants.

For patients in the computer arm the model will calculate the dose with the highest probability to reach the specified concentration target.

For all concentrations a predictive error will be calculated and this will be the primary endpoint that the statistics will be calculated on.

All patients will be followed for between 8 to 12 weeks post-transplant, according to center praxis.

Inclusion Criteria:

• renal transplant recipients using tacrolimus as part of their immunosuppression
• above 18 years
• signed informed consent

Exclusion Criteria:

• no specific