Nosocomial pneumonia is a common complication in patients on mechanical ventilation and results in significant mortality. Diagnosis of pneumonia in patients who are intubated and under mechanical ventilation is difficult, even with the aid of clinical, laboratorial, and endoscopic tests. The objective of this study was to compare three methods of tracheal sputum collection in patients with a clinical and radiological diagnosis of pneumonia. Twenty-two patients with a clinical diagnosis of liver disease were enrolled, 18 years of age or older, 13 males and nine females, who had been mechanically ventilated over an intubation period of 5.86 ± 4.62 days. These patients were being treated in intensive care unit (ICU) of the Liver Transplantdepartment. Secretion collection was carried out according to a protocol with three distinct methods: endotracheal aspiration with a closed aspiration system, Bal cath and bronchoalveolar lavage. Of the 22 patients analyzed, 21 (95.4%) showed one or more infectious agent when the closed aspiration system was used. With the Bal cathâ collection, 19 patients (86.3%) had one or more infectious agents; in the collection by bronchoalveolar lavage, 10 patients (45.4%) presented one or more infectious agent. According to the laboratorial analysis, 14 different microorganisms were isolated, the most frequent of which were Staphylococcus aureus, Pseudomonas aeruginosa, and Klebsiella pneumoniae. We concluded that aspiration with the closed system produced the most effective results in comparison with those of bronchoalveolar lavage and the Bal cathâ, and may be an acceptable method for diagnosing hospital-acquired pneumonia when no fiberoptic technique is available.