Although primary antifungal prophylaxis (PAP) is routinely administered in patients with acute myeloid leukemia (AML) during remission-induction and consolidation chemotherapy, the impact of PAP on the incidence of invasive fungal infections (IFIs) is not well described. We retrospectively analyzed the incidence of IFIs in 152 patients with AML who had been admitted to a tertiary cancer center between August 2009 and March 2011 and received PAP within 120 days after first remission-induction chemotherapy. We excluded patients who had undergone stem cell transplantation. Patients received a PAP drug with anti- Aspergillus activity during 72% (7,660/10,572) of prophylaxis-days. The incidence of documented IFIs (definite or probable according to revised European Organization for Research and Treatment of Cancer [EORTC] criteria) was 2.0/1,000 prophylaxisdays (95% confidence interval [CI], 1.23 to 3.04). IFIs due to molds were more common than IFIs due to yeasts (1.5/1,000 prophylaxis-days versus 0.4/1,000 prophylaxis-days; P 0.01). Echinocandin-based PAP (8.6 and 7.1/1,000 prophylaxis-days, respectively) was associated with higher rates of documented IFIs than anti-Aspergillus azoles (voriconazole or posaconazole) (2.4 and 1.1/1,000 prophylaxis-days, respectively) at both 42 days (P 0.03) and 120 days (P<0.0001) after first remission-induction chemotherapy. The incidence of overall (documented and presumed) IFIs (P<0.001), documented IFIs (P<0.01), and empirical antifungal therapies (P<0.0001) was higher during the first 42 days than after day 42. Despite the broad use of PAP with anti-Aspergillus activity, IFIs, especially molds, remain a significant cause of morbidity and mortality in AML patients, predominantly during the remission-induction phase. Patients receiving echinocandin-based PAP experienced higher rates of IFIs than did those receiving anti-Aspergillus azoles.