Between January 1, 1984, and December 31, 1988, 35 patients at the Los Angeles County + University of Southern California Burn Center had postoperative cultures from their burn wounds that grew Aspergillus species; clinical burn-wound aspergillosis occurred in 66% of these cases and death occurred in 53% of these cases. Beginning in November 1984, several modifications in the air-conditioning system and topical antimicrobial wound therapy were undertaken. Cleaning and 8Cu-quinolinolate treatment of air ducts every 2 months did not reliably clear Aspergillus species from the air in patient care areas. Several changes in topical therapeutic regimen failed to prevent both burn wound culture positivity and clinical aspergillosis. Finally, installation of high-efficiency particulate air filters, installation of new air ducts, and inception of wound irrigation with a solution of mafenide hydrochloride plus nystatin both during and after operation were associated with a reduction in wound culture positivity rate to one occurrence in 1988 (Poisson probability less than 0.01 versus the rate in 1984) and no occurrences during the 18 months after the false ceiling of the burn ward was sealed.