Currently at the University of Florida, 22/45 children and adolescents are long-term survivors in complete sustained remission of standard chemotherapy regimens and central nervous system prophylaxis. All such therapy was discontinued in these survivors at 36 months after diagnosis and they were given monthly inoculations of BCG of the Tice strain by tine technique. 19/22 of BCG-treated patients remain in remission for 12 to 44 + months after cessation of chemotherapy. 1/22 has suffered relapse. Immunological function tests have shown statistically significant increased lymphocyte responses to PPD in contrast to age-matched controls and normal siblings. A trend to earlier than expected return to normal in other immunological parameters, including absolute lymphocyte counts, intradermal skin tests, phagocytosis indices, PHA transformation, and E-rosette forming cells was also observed, coincident with the BCG treatment. Further study of the role of BCG in acute lymphoblastic leukemia patients after cessation of chemotherapy is encouraged.