The efficacy and safety of preemptive therapy using ganciclovir (GCV) 5 mg/kg once daily for CMV infection after unrelated cord blood transplantation (CBT) were studied. The initial preemptive therapy with GCV 5 mg/kg once daily led to resolution of CMV antigenemia in 25 of 34 patients (74%). In the remaining 9 patients (26%), antigenemia resolved after dose-escalation of GCV or change to foscarnet therapy. Recurrence of antigenemia was seen in 18 patients (53%). A total of 12 patients received the second preemptive therapy with GCV 5 mg/kg once daily, which led to resolution of antigenemia in 11 of 12 patients (92%). The remaining 1 patient (8%) required change to foscarnet therapy. None of 34 patients developed CMV disease. Neutropenia with an absolute neutrophil number of less than 1 and 0.5 x 10(9) per liter after GCV therapy occurred in 12 (35%) and 1 (3%) patients, respectively, after the initial therapy, and in 2 (17%) and 0 (0%) patients, respectively, after the second therapy. No patients developed neutropenic fever or secondary graft failure after GCV therapy. There were no deaths directly attributable to GCV therapy. The present study suggests that antigenemia-based preemptive strategy using GCV 5 mg/kg once daily is feasible and effective for CBT recipients.