Risk factor for invasive pulmonary aspergillosis in HIV-negative patients include neutropenia, corticosteroid therapy, and chemotherapy. Corresponding risk factors in HIV-positive patients have not yet been reported. A case-control study was conducted at the Bichat-Claude Bernard Teaching Hospital, Paris, France, between 1991 and 1996. Eight cases were identified. In three cases, the diagnosis was documented histologically. Of the remaining five patients, four had a de novo lung cavity with a positive bronchoscopy sample, and one had a pulmonary infiltrate with a positive bronchoscopy sample in the absence of any other potential pathogen. Each case was matched with three controls who were admitted during the same period and had CD4 counts lower than 50/mm3. Median age was 38.1 years in the cases and 38.4 years in the controls. Median CD4 counts were 12.5 +/- 19.2 in the cases versus 19.3 +/- 16.3 in the controls (P = 0.14). No case-control differences were found for AIDS duration, neutrophil counts at diagnosis or during the previous six months, history of corticosteroid therapy or chemotherapy, or number of previous opportunistic infections. Cases were more likely than controls to have a preexisting lung cavity (3/8 versus 0/24; P = 0.01) and had spent more time in the hospital during the previous year (7 +/- 4.5 versus 2.8 +/- 3.2 weeks; P = 0.02). These data do not support a role for neutropenia or immunosuppressive treatments as risk factors for invasive aspergillosis in AIDS. They suggest that AIDS patients with a lung cavity or frequent hospital stays are at increased risk for invasive aspergillosis.