A Study to Compare How the Body Absorbs and Processes Two Different Formulations of the Anti-rejection Medication Tacrolimus (Advagraf® or Prograf®) in Children Receiving an Organ Transplant, and How Safe and Effective They Are Over a Longer Period of Time

Inclusion Criteria: * The subject is aged \<16 years of age, undergoing primary liver, kidney or heart allograft transplantation * The subject must be able to swallow intact Prograf® or Advagraf® capsules * Subjects, treated since transplantation with Basiliximab or ATG/ Mycophenolate Mofetil (MMF)/steroids, whose gastric motility has resumed and whose renal function is adequate on Day 1 (Heart only) Exclusion Criteria: * Subject is receiving a multi-organ transplant or has previously received an organ transplant (including re-transplantation) * Subject with pulmonary vascular resistance ≥4 Wood units despite medication * Subject with significant renal impairment, defined as having serum creatinine ≥230 μmol/l (≥2.6 mg/dl) pre-transplantation. (Not applicable for renal transplanted subjects) * Subject with significant liver disease, defined as having continuously elevated SGPT/ALT and/or SGOT/AST and/or total bilirubin levels of ≥3 times the upper value of the normal range of the investigational site during the past 28 days. (Not applicable for liver transplanted subjects) * Subject with malignancies or a history of malignancy within the last 5 years, with the exception of those with basalioma or squamous cell carcinoma of the skin that has been treated successfully. (Not applicable for transplanted subjects with a primary organ diagnosis of cancer) * Subject requiring systemic immunosuppressive medication for any other indication than transplantation