We carried out a prospective study on galactomannan enzyme immuno assay (GEI) (Platelia Aspergillus EIA, Bio-Rad) testing for diagnosis of invasive aspergillosis (IA) in serum and broncho-alveolar lavage (BAL) in 200 patients with hematological malignancies and profound neutropenia. The incidence of proven and probable IA was 6% and 5.5%, respectively. In patients with fever or pneumonia, a single-positive GEI test result (galactomannan index >or= 0.5) had excellent specificity (100%). Sensitivity was relatively low (40%) at onset of fever, but increased to 94.7% after 6 days of fever. In patients with infiltrates in chest X-ray or computed tomography scan (n = 48), GEI testing in BAL had a favorable diagnostic accuracy as compared with GEI testing in serum (sensitivity 100% versus 71%). Our findings indicate that antifungal therapy should be started immediately at onset of fever in neutropenic patients with positive GEI tests. In patients with fever refractory to broad-spectrum antibiotics (>or=6 days of fever), the high diagnostic accuracy makes GEI testing a valuable diagnostic tool and questions the common strategy to carry out antifungal treatment irrespective of diagnostic testing in this situation. Our data also show that GEI testing in BAL can be useful for early diagnosis of IA in patients with hematological malignancies and pulmonary infiltrates.