In patients with rheumatoid arthritis the appearance of neoplastic disease has been fundamentally described of lymphoproliferative origin. The case of a 59 year old woman with rheumatoid arthritis of a 4 year evolution is reported. The patient was treated with gold salts and methotrexate and presented successively a bronchogenic carcinoma and a non-Hodgkin lymphoma. The epidemiologic studies in the relation of rheumatoid arthritis-neoplasia are discussed and the pathogenic hypotheses to the immune alterations as well as the treatments employed are described.