Early diagnosis and prompt introduction of effective therapy are imperative to manage systemic, often fatal adenoviral (AdV) disease following hematopoietic stem cell transplantation (SCT). We evaluated the usefulness of real-time polymerase chain reaction (PCR) in the diagnosis of AdV disease in SCT recipients. Seven SCT recipients, including three with AdV disease, were retrospectively evaluated for AdV genome detection. In serum specimens, the AdV genome was detected at >10(3) copies/ml in the pre-SCT period in two of the five recipients studied. These two patients subsequently developed AdV disease. The three patients with AdV disease had high levels of >10(5) copies/ml during the 4-6 weeks post-SCT period. In none of these patients was the AdV genome detected in urine specimens in pre-SCT period. However, three recipients with detectable urinary levels during the period 1-2 weeks post-SCT subsequently developed AdV disease. Regarding the outcome, two of the three patients with AdV disease died of progressive renal failure. Our results suggest that quantitative determination of the AdV genome in serum and urine is useful to identify patients at high risk of developing AdV disease. Prospectively applied, these measures are expected to improve the dismal outcome of AdV disease in SCT recipients.