Treatment regimens of patients with active cytomegalovirus (CMV) disease require 2-3 weeks of intravenous ganciclovir (GCV) with/without CMV hyperimmune globulin. Oral GCV is effective as a prophylactic agent in prevention of CMV disease. Here we explored the utility of oral GCV as a treatment of active CMV disease. Fifteen renal allograft recipients (CMV donor+/recipient- [53%], CMV donor+/recipient+ [40%] or CMV donor-/recipient+ [7%]) developed active CMV disease. Cytomegalovirus polymerase chain reaction (CMV-PCR) tests were performed at the time of presentation and patients were treated with oral ganciclovir 1 g tid (adjusted for renal function). Patients were monitored for efficacy of treatment by assessment of clinical symptoms and CMV-PCR. Treatment was continued until the CMV-PCR copy number was negative and symptoms resolved. The mean CMV-PCR copy number at the time of diagnosis was 580 copies/microg DNA (nl: < 5 copies/microg DNA). After 5-7 days of treatment, the mean copy number was 65 copies/microg DNA. Fourteen of 15 patients responded well to oral ganciclovir, with complete resolution of clinical symptoms and eradication of CMV-PCR positivity. One patient did not respond to oral ganciclovir therapy due to probable noncompliance. Our data suggest that oral ganciclovir treatment, coupled with careful CMV-PCR monitoring, may be a reasonable alternative to long-term intravenous ganciclovir.