We reviewed our 20-year experience with infant acute lymphoblastic leukemia (ALL). Nine infants (4.2% of all ALL) were identified; all were < 6 months of age. White blood cell counts ranged from 42,000-1.6 million/microL, 6 of 8 had hepatosplenomegaly, and 6 of 9 (66.6%) had central nervous system disease. Of 7 with cytogenetic information, 6 (85.7%) had diploidy; the remaining child was 47, XY,+8,del(21)(q22). Four had the MLL-11q23 abnormality. All received chemotherapy. Four underwent stem cell transplantation. Survival was 67%, (15 months-21 years). Deaths occurred at 9 months, 15 months (graft vs. host), and 7 years (complications of small bowel transplantation). Only 1 undergoing stem cell transplantation died. There were no late recurrences or second malignancies. Despite extensive disease and age < 6 months at diagnosis (a poor prognostic feature), for ALL patients our 67% survival is at least as good as reported, although it is less favorable than childhood ALL.