We conducted a prospective study in the multidisciplinary pediatric intensive care unit (pediatric ICU) of a tertiary-care university hospital in order to determine the incidence, risk markers, risk factors, and complications related to bacterial nosocomial pneumonia (BNP) and tracheitis (BNT) in children. A cohort of 1,114 consecutive admissions to the pediatric ICU was enrolled over a 56-wk period; 154 cases were excluded mostly (75%) because they already had a respiratory infection at entry. The final sample included 960 admissions (831 patients). Diagnosis of BNP or BNT was based on Centers for Disease Control of Atlanta criteria using a consensus method involving three experts, who also attributed complications to BNP and BNT. A total of 29 BNP and BNT (3.0%; 95% CI: 1.1 to 4.1%) were diagnosed (BNP: 1.2%, 95% CI: 0.7 to 1.9%; BNT: 1.8%, 95% CI: 0.8 to 2.6%). Three factors were retained by multivariate analysis as independent risk factors or markers for BNP (immunodeficiency, immunosuppression, and neuromuscular blockade), and two for BNT (head trauma and respiratory failure). Gram-negative bacteria and Staphylococcus aureus were the microorganisms most frequently found in the tracheal aspirates. Prescription of antibiotics was commonly attributable to BNP (75%) and BNT (59%). Death, as well as multiple organ system failure, resulted from BNP in 8% of cases, but never from BNT. In BNT, the reintubation rate was 24%. Nosocomial bacterial respiratory infections are rare in critically ill children. However, BNP causes significant complications, and more attention should be focused on BNT in the critically ill child.