Two anatomoclinical observations of lymphomatoid granulomatosis are reported. The first case concerns a patient presenting a cutaneous localisation and a severe pulmonary infection with acute febrile dyspnea and macronodular opacities seen in pulmonary radiographs. The treatment associating cortisone and chlorambucil led to a complete remission. Five years later a pulmonary recurrence was treated successfully with the same association. The second patient presents dyspnea upon progressive effort, a radiologic and functional syndrome of interstitial involvement. In the absence of precise diagnosis after pulmonary biopsy, the patient was treated with corticosteroids. Four months later, encephalitic damage led to death. In the 2 observations, the biopsies or autopsic samples from the lungs or brain showed necrotic nodular lesions. Bordering on the necrosis, the small arteries and veins are strictured or obstructured by an infiltrate of lymphocytes, plasmocytes, histiocytes, and large cells with atypical nucleus. The ultrastructural examination of the 2 pulmonary biopsies shows the reactional polymorphic nature of the lymphoid infiltrate, the generally imprecise nature of atypical large cells and the modifications of vascular elastic limitations. The blades of elastine are surrounded by microfibrillar material. These different data are compared with those in the literature.