Objective: To study the effect of L-asparaginase therapy when used in combination with other antileukemic drugs, on L5178Y murine leukemia with regard to sequence and order of drug administration. Approach: Study additive, synergistic or antagonistic effects of Asn'ase on treatment with MTX, Ara-C, 6-MP, 5-FU, prednisone and vincristine in mice bearing L5178Y leukemia, using: a) different doses of Asn'ase and other drugs, from therapeutic to toxic; b) different sequences of Asn'ase administration with respect to other drugs; c) different time periods between drugs.