To evaluate the effects of airborne Aspergillus contamination during and after the renovation work of a Florentine haematology unit, we conducted (November 2003-January 2005) a strict programme of environmental fungal surveillance. Air samples were taken from patients' rooms, along the corridors inside the wards, along the corridor between wards and outside the building. The concentration of Aspergillus fumigatus was high along the corridor between the two haematology wards (2.98 CFU m(-3)), lower in the non-neutropenic patients' rooms and outside the hospital building (1.53 and 1.42 CFU m(-3), respectively), very low in the neutropenic patients' rooms (0.09 CFU m(-3)). During this period, three proven cases (A. fumigatus), two probable ones and two possible cases of invasive pulmonary aspergillosis were documented in 97 patients with acute leukaemia (7%). The three cases of proven aspergillosis coincided with the period of renovation work and with the period in which we have found the maximum concentration of A. fumigatus along the corridor. These data suggest a possible relationship between environmental fungal contamination and the incidence of invasive aspergillosis, and underline the importance of environmental surveillance.