Abstract: Using the MMPI program and 3-D high resolution molecular modeling system, a preliminary structure-activity relationship (SAR) based upon molecular shape analysis has been developed for a set of 20 4-R-3, 3-dialkylphenyl-triazenes for which antitumor potency against L1712 Leukemia in mice is reported. The SAR suggests that for antitumor potency, here is a significant difference between the shapes of the active and inactive molecules.