A retrospective study of 37 patients with haematological malignancy (21 acute myeloid leukaemia, 11 acute lymphoid leukaemia, two lymphoma, two hairy cell leukaemia, one Hodgkin's disease) and histologically documented mucormycosis was conducted to evaluate the clinical characteristics and ascertain the factors which influenced the outcome from mycotic infection. Patients were admitted to 18 haematology divisions in tertiary care or university hospitals in Italy between 1987 and 1995. Fever, thoracic pain, dyspnoea and cough were the most frequent presenting symptoms. At the onset, 89% patients were neutropenic (neutrophil counts < 0.5 × 109/l) with a median duration of previous neutropenia of 14 d (range 6–60). The most frequent sites of infection were lungs (81%), CNS (27%), sinus (16%), liver (16%) and orbital space (10%). Only three patients were asymptomatic. A correct in vivo diagnosis was made in only 13 (35%) patients. When performed, thoracic and cranial CT scan were the most useful diagnostic investigations. Despite the fact that 26 febrile patients were treated with empirical antifungal treatment, 28 of the 37 patients (76%) died from fungal infection at a median time of 17 d from the onset of clinical symptoms. Nine patients were cured by antifungal therapy plus, in five cases, radical surgery procedures. An analysis of factors influencing outcome demonstrated that the resolution of chemotherapy‐induced neutropenia and prolonged treatment with amphotericin B and, if feasible, radical surgical debridement treatment, were significantly correlated with recovery from infection. Mucormycosis, a rare filamentous fungal infection that occurs most frequently in neutropenic acute leukaemia patients, is characterized by a high mortality rate. Extensive and aggressive diagnostic and therapeutic procedures are essential to improve the prognosis in these patients.