Investigators set up at the University Hospital of Rennes, a database of more than 300 patients with LGL leukemia from major French services that support this disease, and published in 2010 the largest series of patients in the world (n = 229). However, the limited heterogeneity and retrospective data collected, as all previously released, makes it difficult the proposal of consensual treatment options. If first and second line treatments are based on the use of immunosuppression with methotrexate, cyclophosphamide, or cyclosporin A, no molecule has proven superiority over others. Methotrexate and cyclophosphamide are mainly used in the first line. Invetigators just have in the literature data on about 100 patients treated with either of these drugs. Combining the results of our series with those in the literature, invetigators estimate the respective overall response rate (RG) and complete response rate (CR) in 55% and 30% for methotrexate, and 60% and 50% for cyclophosphamide.