A multi-center two phase, double-blind, placebo controlled, randomized prospective study of 130 lung transplant recipients. Patients will be screened and consented prior to transplant. All consented patients will receive IV ganciclovir within 24 hours of transplant for not more than 14 days. Patients will enroll in Phase I of the study is an open label safety and efficacy analysis of three months of oral valganciclovir in adult transplant recipients who are at risk for CMV. After completion of 3 months of open label therapy, patients that meet the criteria for Phase II of the study will be randomized to 9 months of blinded therapy (Placebo/Valgan). Phase II of the study is designed to assess the efficacy of short course sequential IV ganciclovir followed by oral valganciclovir as compared to the extended period of oral valganciclovir prophylaxis in the prevention of CMV disease in at risk lung transplant recipients