We verified whether a clinical score system developed for renal transplant patients predicts the severity and outcome of cytomegalovirus interstitial pneumonia (CMV IP) in allogeneic bone marrow (BMT) recipients. The score system was retrospectively applied to 20 patients at the estimated date of onset of IP and 10-14 days later. Seven patients received ganciclovir (GCV), seven received GCV plus intravenous immunoglobulin (i.v. Ig), and six received only supportive care. Nine out of 14 patients who received GCV with or without i.v. Ig survived the episode of IP (the median score of these patients at diagnosis of CMV IP was 5 (range 3-8)), while the remaining five patients died of respiratory failure during IP and at the diagnosis had a median score of 10 (range 9-11) (P=0.01). The six patients who received only supportive care survived for a median time of 21 days (range 10-24 days) from the estimated onset of CMV IP, and the median score at the diagnosis of IP was 10 (range 8-12). The overall survival correlates strongly with low initial severity of IP as measured by this score system: 11 out of 20 patients who died of respiratory failure during IP had at the estimated onset of IP a score >8, while of the nine patients who survived IP, eight had at the onset a score <7 and the remaining one a score of 8 (P=0.0007). The sensibility, specificity, predictive positive value and predictive negative value of the score system (with a threshold value of 8) to identify patients who survived IP was: 100%, 88%, 91% and 100%, respectively. The use of ganciclovir alone or in combination was the most important determinant of outcome. These data support the relevance of this score system with a threshold value of 8; if prospective and controlled studies confirm our observations, it would help physicians to identify BMT recipients during CMV IP with high vs. low risk of poor outcome.