After reviewing the immunological anomalies provoked by the human immuno-deficiency virus (HIV) as well as their implications in pulmonary pathology, the authors enumerate the diagnostic and therapeutic methods currently available in the treatment of patients suffering from AIDS and pulmonary diseases. The clinical features as well as the chest radiograph--an essential first line tool--may lead to atypical features. Respiratory function tests and scintigraphy to Gallium may be a useful additional diagnostic technique but for a full pulmonary investigation a bronchoalveolar lavage is required and/or transbronchial biopsy. Open lung biopsy is rarely required, and then only as a last resort. The treatment of pneumocystis remains centred on Trimethoprim sulfamethoxazole and Pentamidine, with a similar efficacy (80% care) but both have side-effects which are less frequent but more severe with Pentamidine. Administration of Pentamidine by aerosol, Eflornithine and Trimetrexate are under study. The level of lactic dehydrogenase (LDH) seems to be a prognostic factor. The value of prophylaxis is discussed. If the treatment of tuberculosis, an infection which is seen more and more frequently, still rests on classical triple therapy, the treatment of atypical mycobacterial infections is even more deceptive than in non-immuno-suppressed hosts. The same is true with pneumonia due to cytomegalovirus. The treatment of lymphoid interstitial pneumonia which is probably a direct result of HIV infection, remains controversial. On the other hand, pulmonary Kaposi's sarcoma is associated with an elevated mortality, and all treatment (interferon and chemotherapy) is disappointing.