An analysis based upon structure-activity relationships (SAR) of the COX-2-inhibiting properties of flavonoids, a group of potential cancer chemopreventative agents, reveals that there is a dual structural basis for these activities. Each of these structural determinants (pharmacophores) alone is sufficient for activity. One of the pharmacophores is a 2D 6.9 A distance descriptor that spans the A and C rings and includes the 4-OXO and 7-hydroxyl moieties. The potency associated with that pharmacophore is determined by a series of structural modulators that can increase, decrease, or even abolish the COX-2-inhibiting potential associated with that pharmacophore. The second pharmacophore describes a para-substituted phenolic B ring that requires unsubstituted meta and ortho positions. Based upon this, it indicates that hydroxylation at the 4'-position and a free 5'-position are sufficient for COX-2-inhibiting activity. The potency associated with this pharmacophore is modulated by log P2 and by the molecular weight.