Reducing and even omitting doses of MTX due to regimen related toxicities (mucositis, hepatic and renal toxicities) is common. However, dose reduction of MTX may be associated with increased risk of acute GVHD and early death. Several non-randomized studies have shown that folinic acid (FA, leucovorin) administration may reduce MTX toxicity. Nevertheless, the efficacy and safety of its administration remain controversial. Despite limited and uncontrolled data, the European Group for Blood and Marrow Transplantation (EBMT) and the European LeukemiaNet working group recently recommended the use of FA-rescue and proposed a uniform policy of FA-rescue 24h after each MTX dose: 15mg every 8h after MTX administration on day 1, and every 6h on days 3, 6 and 11. Yet, according to several surveys (including by EBMT-ELN) only half of bone marrow transplantation (BMT) centers use to give post MTX FA-rescue.