Tarurine mustard, N-bis-(2-chloroethyl) aminoethane sulfonic acid, had significant chemotherapeutic activity against the P388 and L1210 lymphocytic leukemias, and the pigmented and unpigmented B16 melanomas. Its cytotoxicity toward the P388 in primary culture (IC50=50muM) was not reduced by a high taurine concentration (5 mM). Taurine also did not reduce its efficacy in vivo. However, in vivo, taurine protected against neurotoxicity, intestinal necrosis, pulmonary emboli formation and tail vain necrosis when administered i.v. with taurine mustard.