The pharmacological properties (toxicity and antitumor activity against W256 carcinosarcoma and L1210 leukemia) of thirty five new triazenes derived both from amides and esters of 3-methyl-4-amino-benzoic acid and from aromatic dipeptidic esters were investigated. The new compounds proved to be moderately effective against W256 carcinosarcoma and totally devoid of activity against L1210 leukemia, except for ethyl,4-(3,3-dimethyltriazenophenyl)-N-alpha-(9-fluorenyl)-acetyl-L-alanine ester which exhibited borderline activity against this leukemia. The pharmacological data thus obtained were correlated with the physico-chemical parameters of the new triazenes in a quantitative structure-activity relationship (QSAR approach). The results of the computed equations suggested that the electronic and the lipophilicity factors alone are not sufficient to give a satisfactory picture of the in vivo behavior of such compounds.