The pharmacokinetic properties of immunosuppressive drugs are quite different in newborns than in adults and few studies describe the pharmacokinetics of these drugs in pediatric heart transplant recipients. We report on the two-year follow up of a neonate who underwent heart transplantation for Hypoplastic Left Heart Syndrome on day of life 9. Two different immunosuppressive regimens were used: cyclosporine, azathioprine and prednisone in the early postoperative period, followed by the routine tacrolimus and mycophenolate mofetil combination plus prednisone from post-transplant day 22. Our findings demonstrate marked variability in immunosuppressive pharmacokinetic profiles early post-transplant. Frequent monitoring of drug levels is required to ensure that they remain within the therapeutic range. After the first 2-3 months post-transplant, changes in immunosuppressive drug levels are less marked and correlate more with the administered dosage.