The variable absorption of Cyclosporine A, especially in pediatric patients, has complicated its use in the immunosuppressive therapy of solid-organ transplant recipients. In response, a microemulsion formulation of cyclosporine A has been developed to minimize this variability. As stable pediatric solid-organ transplant recipients are converted from Sandimmune to the microemulsion formula, Neoral, cyclosporine formulations, the dosage, blood cyclosporine level, and serum chemistries will be monitored in a prospective manner, to evaluate.