The synthesis, physicochemical characterization and preliminary pharmacological evaluation of the cytotoxic effects of two novel substances, 1-(4-benzoylphenyl)-3,3-dimethyltriazene and 1-(2-benzoylphenyl)-3,3-dimethyltriazene is presented. The cytotoxicity of the novel benzophenone-linked triazenes and of ten other 1-phenyl-3,3-dimethyl triazene derivatives as well as of the referent alkylating drug melphalan was assessed using the MTT-dye reduction assay. A panel of human tumor cell lines was used: the chronic lymphoid leukemia SKW-3, the acute promyelocyte leukemia HL-60 and its multi-drug-resistant subline HL-60/Dox. Both novel compounds showed strong cytotoxic activity, comparable to that of the referent alkylating agent melphalan, whereas the ten ring-substituted 1-phenyl-3,3-dimethyl triazenes proved to be far less active in vitro. DNA-fragmentation analysis indicated that after 24 h treatment the novel benzophenone-linked triazenes induced programmed cell death in HL-60 cells.