In the aetiological diagnosis of pulmonary infections in patients affected by haematological malignancies we evaluated the utility of bronchoalveolar lavage (BAL). One hundred and twenty-seven BAL were performed in 119 patients. In our series, we identified the agent of pneumonia in 53.5% of episodes with the best results in aspergillosis, very common in these patients. The previous empirical anti-infective treatment was modified in 14 episodes (11%). The procedure was generally well tolerated and only one patient bled. We maintain that BAL is a useful diagnostic tool for detecting the agents of pulmonary infections in patients with haematological malignancies, especially when the routine microbiological procedures fail, and it also represents a good alternative to more invasive procedures.