The present study investigated the improvement in the diagnosis of invasive pulmonary aspergillosis (IPA) adding a molecular test on bronchoalveolar lavage (BAL) to the routine diagnostic approach including microscopy, culture and galactomannan (GM) immunoassay. A total of 133 BAL samples were retrospectively tested for the Aspergillus DNA: 112 samples were from immunocompromised patients at risk of invasive fungal infection and 21 were from patients not at risk and without clinical evidence of IPA. The latter samples were used to identify the cut-off of positivity for the molecular test. Applying the cut-off quantity of 50 copies/reaction, the PCR test had 90% sensitivity and 97% specificity and resulted the most sensitive, specific and accurate among those evaluated. The statistical analysis showed that the probability that a patient is not affected by IPA is 99% when the three tests (PCR, GM and culture) are concordantly negative.