Isolation of patients at risk of invasive mould infection might be suitable for the reduction of invasive aspergillosis or zygomycosis, if combined with high-efficiency particulate air filtration. Prophylactic wearing of filtering masks of N95 or FFP2 standards has not yet been demonstrated to be efficacious in reducing invasive mould infections outside of scenarios with excessive contamination of room air by fungal spore-loaded dust. The oral broad-spectrum antifungal azoles posaconazole and voriconazole offer protection against invasive Aspergillus infections in severely neutropenic leukaemia patients and allogeneic haematopoietic stem cell transplant recipients; however, their routine use might result not only in considerable side effects, but also in the spread of multi-azole-resistant Aspergillus species, so that careful selection of suitable high-risk patient populations is mandatory.