During a 15-month retrospective clinical study in an academic referral-based cancer center, 26 patients with S. maltophilia respiratory tract infections were identified (which were associated with bacteremia in 13 patients). Five of these 26 patients had previously undescribed sinopulmonary involvement. The infections were typically nosocomial. Nine patients with solid tumors had malignant involvement of the respiratory tract (five with obstruction). In two patients, the infection co-existed with pulmonary aspergillosis. Fifteen patients (58%) died of the infection. The factors that correlated with a poor outcome included bacteremic pneumonia, persistent neutropenia, presence of obstruction, development of septic shock or multiple organ dysfunction, and delay in institution of appropriate antibiotic therapy. In multivariate analysis, only septic shock and delayed therapy remained significant. Trimethoprim-sulfamethoxazole and/or ticarcillin-clavulanate were most commonly associated with a favorable outcome.