The incidence rates of opportunistic diseases, hospital admission and death have fallen markedly since the advent of highly active antiretroviral therapy (HAART). We examined the impact of HAART on the pattern of HIV-related respiratory diseases necessitating hospitalization. We retrospectively compared the numbers and etiologies of respiratory diseases diagnosed in HIV-infected patients hospitalized in the chest department of a Paris university hospital during the three years preceding widespread prescription of HAART in France (era 1, starting in July 1993) and the first three years of widespread HAART prescription (era 2, starting in July 1996). Respectively, 207 and 119 HIV-infected patients were admitted for respiratory disease in era 1 and era 2. Only 31.1% of patients admitted during era 2 were receiving HAART. Pulmonary opportunistic infections other than Pneumocystis carinii pneumonia (PCP) (p = 0.0008) and exacerbations of chronic bronchial disease due to gram-negative bacilli (p = 0.04) virtually disappeared in era 2. In contrast, PCP, bacterial pneumonia, tuberculosis, pulmonary Kaposi's sarcoma and pulmonary non-Hodgkin lymphoma showed only a twofold decrease in era 2, while lung cancer was more frequent (p = 0.004). The frequency of severe respiratory diseases necessitating hospitalization of HIV-infected patients has fallen since the advent of HAART, and their etiologic distribution has changed.