BACKGROUND Mycoses are common complications of haematological neoplasias. For successful antimycotic treatment, a knowledge of preferential underlying disease, frequency, species and site of the mycosis is of importance. METHODS Postmortem material comprising clinical data, autopsy protocols and histological sections obtained between 1976 and 1990 from 1,053 patients with leukaemia and malignant lymphomas following antineoplastic therapy was analysed retrospectively. RESULTS Autopsy revealed systemic mycoses in 184 patients (17.5%). Between 1976 and 1990, the incidence of fungal infections increased from 12% to 30%, most being found in acute leukaemia (24%). Myeloproliferative syndrome (18%), non-Hodgkin's lymphomas (16%), Hodgkin's disease (10%) and plasmocytoma (2.5%) were less frequently associated with mycoses. With no preference for any particular malignancy in evidence, aspergillosis predominated at histology (85 cases), while candidosis occurred in 75 cases. A combination of two mycoses (aspergillosis and candidosis) (14 patients), zygomycosis (eight patients) and cryptococcosis (two patients) were much less common. While aspergillosis caused mostly pulmonary (81 cases) and cerebral (18 cases) infections, candidosis most frequently affected the GI tract (83 cases). The fungal infection was regarded as the main cause of death in some 76% of the cases. An analysis of bone marrow of patients with mycosis (184 cases) revealed a predominance of hypoplasia (54%) over tumour infiltration (34%) and normal bone marrow (12%). In malignancies with no mycoses (869 cases) in contrast, hypoplasia was significantly less common (19%) than infiltration (59%) or normal bone marrow (22%) (p < 0.001). CONCLUSIONS The incidence of mycoses in haematological neoplasias in our post mortem series has continued to increase. Bone marrow hypoplasia in particular predisposes to fungal infection. The lungs are the organs of predilection, and aspergillosis is likely to be the infection presenting.