Pulmonary mucormycosis (PM) is a life-threatening fungal infection with an increasing incidence among patients with acute leukemia. In some immunocompromised hosts, the reversed halo sign (RHS) has been described on the pulmonary computed tomographic (CT) scan of patients with mucormycosis. Methods. This study reports a single-center experience with PM exclusively in patients with acute leukemia. Clinical records, laboratory results, and CT scans were retrospectively analyzed to evaluate the clinical usefulness of the RHS for the early identification and treatment of PM, with regard to outcomes in these patients. Results. Between 2003 and 2012, 16 cases of proven PM were diagnosed among 752 consecutive patients receiving chemotherapy for acute myeloblastic or lymphoblastic leukemia. At the time PM was diagnosed, all patients but one were neutropenic. The study of sequential thoracic CT scans showed that during the first week of the disease, the RHS was observed in 15 of 16 patients (94%). Initially, other radiologic findings (multiple nodules and pleural effusion) were less frequent, but appeared later in the course of the disease (6% and 12% before vs 64% and 55% after the first week). After the diagnosis of PM, median overall survival was 25 weeks (range, 3-193 weeks), and 6 patients (38%) died before day 90. Conclusions. In the particular setting of neutropenic leukemia patients with pulmonary infection, the presence of the RHS on CT was a strong indicator of PM. It could allow the early initiation of appropriate therapy and thus improve the outcome.