Rhinoorbitocerebral mucormycosis is a rare invasive fungal infection that is fatal when untreated. We describe an immunosuppressed patient with chronic lymphatic leukaemia who developed a severe rhinoorbitocerebral mucormycosis after allogeneic bone marrow transplantation. Due to the potentially fulminant course and fatal outcome, radical excision of the necrotic area in combination with antifungal therapy is necessary in the presence of suspicious clinical signs of mucormycosis despite a lack of histopathologic confirmation.