Cytomegalovirus in solid organ transplant recipients can result in significant morbidity and mortality due to concurrent immunosuppression. Traditionally intravenous followed by oral ganciclovir has been used to prevent and treat cytomegalovirus infection and disease in transplant recipients. Recently a new oral form of ganciclovir, valganciclovir has been approved by the Food and Drug Administration for the treatment of CMV retinitis in patients with AIDS. Valganciclovir is more bioavailable and requires fewer daily doses and lower pill burden than oral ganciclovir. In addition valganciclovir can attain ganciclovir plasma levels similar to intravenous ganciclovir. This protocol will test the ability of valganciclovir to provide similar drug exposure (area under the curve, AUC) as oral and intravenous ganciclovir at equivalent doses in the setting of kidney and kidney-pancreas transplantation. Patients will receive four different dosing/dosage form schemes. Intravenous ganciclovir at 2.5mg/kg every 12 hours, which is the usual treatment at this facility post surgery will be administered for approximately 7 days (phase I), then patients will receive valganciclovir 900 mg daily for 7 to 21 days (phase II), then patients will receive 450 mg daily for at least 4 days (phase III), and finally, ganciclovir 1000 mg every 8 hours for at least 4 days (phase IV). Serial blood samples will be collected for pharmacokinetic analyses after each change in dose/dosage form (after each phase). After completion of the study, patients will be maintained on valganciclovir 450 mg daily for CMV prophylaxis or oral ganciclovir for a length of time prescribed by the transplant surgeon. By characterizing the pharmacokinetics of valganciclovir in kidney/pancreas transplant patients, it is hoped that appropriate dosing to prevent CMV disease and limit toxicity may be achieved.