Primary lung lymphomas are uncommon and the use of immunohistochemical and molecular biological techniques have widely contributed to their understanding. Generally, they are of low grade malignancy and most develop from mucosa-associated lumphoid tissue (MALT). Cellular analyses of samples obtained routinely by endoscopy (transbronchial biopsy or bronchoalveolar lavage) will probably enable the clinician to avoid invasive diagnostic procedures, such as surgical lung biopsy. Treatment of limited forms is usually surgical. As to bilateral forms or those with lesions of other mucosae e.g. gut, the best therapeutic strategy remains to be defined.