Each patient will receive 900 mg of Valcyte® daily with food for the period specified in that center (typically 100 days), starting as soon as possible after the transplant. According to routine practice, intravenous ganciclovir (5 mg/kg) may be substituted if the patient is unable to tolerate oral medication, during which time the patient will not be enrolled into the study. The dose of Valganciclovir may be reduced or interrupted at the discretion of the Investigator if he, or she, suspects that ganciclovir-related toxicity has occurred, or if the estimated creatinine clearance of the patient drops below 60 ml/min For the actual study, each patient will receive 2 days treatment on consecutive days with each Valganciclovir syrup formulation (900 mg once a day.) and the tablet formulation (900 mg once a day) in a randomized order, before continuing with Valcyte® prophylaxis (commercially available tablets). The following three treatments will be administered in this study: Randomization will occur through the IDS pharmacy and a computerized system will randomize the subjects.