The outcome of adenovirus (ADV) infections in adult hematopoietic stem cell transplant (HSCT) patients remains poorly characterized. We studied 14 adults and 3 children, who had undergone HSCT and had developed ADV viremia. Peak ADV DNA levels were significantly higher in patients with ADV diseases than in those without (P=0.03). All children survived the ADV infections. Among the 14 adult HSCT patients, 11 were treated with cidofovir, 2 with ribavirin, and 1 did not receive antiviral treatment. Six of the 13 (46%) treated patients developed ADV diseases and 3 of them (23%) died of ADV infections. Sustained viremia (≥3 positive polymerase chain reaction assays during follow-up) was detected in all patients who finally died of ADV infections. However, 2 adults having had transient ADV viremia either survived or died of diseases other than ADV infections. Our study indicates that the outcome of adult HSCT patients with sustained ADV viremia may be poor, even for those who have received anti-ADV treatment.