Infant ALL is uncommon, biologically distinctive from the disease in older children, and associated with a relatively poor prognosis. Adverse prognostic factors include the presence of an MLL gene rearrangement (observed in up to 80% of infants with ALL), younger age at diagnosis, high presenting leukocyte counts, and slow early response to therapy. The role of stem cell transplant in first remission remains controversial. Current research efforts to improve the outcome of MLL-rearranged ALL in infants include clinical trials testing cytarabine-intensive regimens and translational investigations of novel, targeted therapies, such as FLT3-inhibitors.